Power transfer apparatus having a vibration dampening mechanism which provides structural support for the apparatus

ABSTRACT

A power coupling mechanism having fluid dampening device with interfitting members which assist in the absorption and transmittance of stress due to torsion and thrust loads, thus reducing the size of a bearing supporting relatively rotatable parts.

This application is a division of application Ser. No. 08/382,307, filedJan. 31, 1995, now U.S. Pat. No. 5,617,940.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power transfer apparatus having avibration dampening mechanism, and more particularly, a power transferapparatus disposed between a crankshaft of a power producing device,such as an internal combustion engine, and a power output device, suchas an automotive transmission, for transmitting torque therebetween,where portions of the vibration dampening mechanism provide structuralsupport for the power transfer apparatus in the presence of axialstresses, such as thrust force in an axial direction on the powertransfer apparatus.

2. Description of Related Art

Power transfer apparatus having a pair of flywheels and a clutchmechanism, usually placed between a crankshaft of an engine and atransmission are well known.

For example, there are flywheel assemblies in which two flywheels arecombined to absorb vibration from an engine. One such flywheel assemblyincludes a first flywheel connected to the crankshaft in the engine, asecond flywheel supported by the first flywheel for limited relativerotation therebetween, and a dampening element elastically connectingthe first flywheel to the second flywheel in a circumferential directionfor dampening torsional vibration between the first and secondflywheels. The second flywheel has a friction surface formed on its oneside close to a transmission, and a clutch is fixed to the frictionsurface.

The clutch is comprised mainly of a clutch disk assembly and a clutchcover assembly. The clutch disk assembly has an annular clutch diskwhich selectively contacts the friction surface of the second flywheel,and a hub flange having splines mated with a main drive shaft in thetransmission. The clutch cover assembly includes a saucer-like clutchcover having its exterior circumferential edge fixed to the flywheel, anannular pressure plate enclosed in the clutch cover for pressing theclutch disk against the friction surface of the second flywheel, and adiaphragm spring held by the clutch cover for urging the pressure platetoward the second flywheel.

Disadvantages of the prior art power transfer device will be listedbelow.

1) The flywheel assembly and the clutch separately made, make for alarge number of parts, and costly manufacturing.

2) In disengaging the clutch, the forces associated with the releaseload are transmitted to the second flywheel via the clutch cover. Theforce applied to the second flywheel is then transmitted to a bearingdisposed between the first and second flywheels. The bearing must beable to withstand the forces associated with disengagement of theclutch. Therefore, the bearing must be able to withstand large forcesand still be rotatable. However, such a bearing is expensive andoccupies a large space in radial direction. This impose a greatrestriction upon the design of the interior of the dampening element inthe flywheel mechanism.

3) If the first flywheel of the power transfer device is mounted to adisk-shaped flexible plate which is mounted to the crankshaft, and theflexible plate and the first flywheel are fixed at their respectiveouter circumferences to each other, and a bearing is providedsurrounding a boss of the first flywheel to hold the second flywheelrotatably relative to the first flywheel, then it is difficult to ensureaccurate concentric positioning of the flexible plate with the firstflywheel, and the concentric positioning of other parts.

In another prior art flywheel assembly, a fluid duct filled with fluidis defined by a disk-shaped element within a chamber partially definedby the first flywheel. A dampening element for dampening torsionalvibration is provided within the chamber. The first flywheel has acenter boss extending toward the transmission, and the second flywheelis supported thereon via a bearing which encircles the center boss ofthe first flywheel allowing for limited relative rotation between thetwo flywheels.

The flywheel assembly may be provided with a flexible plate which canflex itself in an axial direction between the crankshaft in the engineand the first flywheel in order to absorb flexural vibration from theengine. The flexible plate has its inner circumferential edge fixed totip of the crankshaft and its outer circumferential edge fixed to theouter circumference of the first flywheel. A plurality of bolts aredisposed circularly at the same intervals. A ring gear to start theengine is fixed at the outer circumference of the first flywheel.

Some of the disadvantages of the flywheel assembly will be listed below:

1) A seal member must be provided between the disk element and a poweroutput element to seal the fluid within the chamber. It is desirablethat a pre-load is applied to the bearing supporting the first andsecond flywheels, and for that purpose, an elastic element must beprovided. As will be recognized, provision of the seal element and theelastic element increases the number of parts, which in turn causes acost to rise.

2) The dynamics of the flywheel assembly are such that flexuralvibration from the engine may produce noise. The damper mechanismrequires a certain level of inertia in order to absorb vibrations. Ifthere is insufficient inertia, the flywheel assembly cannot absorbtorsional vibration from the engine.

3) Since the flexible plate and the first flywheel are fixed at theirrespective circumferences to each other, relative location among theflexible plate and the boss and bearing for the first flywheel aredetermined at the outer circumferences of the flexible plate and thefirst flywheel, and this causes the parts to be less concentric. Thebearing is positioned outside a pitch circle of the bolts, and thisimposes a restriction upon the design of the interior of the damper.

4) A power transfer device system including a damper in an automobilemust increase moment of inertia of a power output mechanism to reduce aresonance frequency to an engine's idling speed or below. However, thering gear to start the engine is fixed to the outer circumference of thefirst flywheel, and hence, a ratio of the moment of inertia of the poweroutput mechanism cannot be sufficiently increased.

In another prior art mechanism, a damper mechanism includes a hubflange, a bearing and a dampening element. A power input element iscoupled to a crankshaft in the engine while the hub flange is coupled toa main drive shaft extending from the transmission, The hub flange has aboss extending toward the transmission and a flange formed at the outercircumference of the boss. The bearing is provided between a powerreceiving element and the hub flange to support both of them rotatablyrelative to each other. The dampening element is provided within a fluidspace to elastically connect the power receiving element and the hubflange in a circular direction and further to dampen torsional vibrationbetween them. A driven plate connecting the dampening element and thehub flange is provided therebetween. The dampening element includes anelastic element provided in a window spreading toward the circumferenceof the driven plate, and a resistance generating mechanism for producingresistance when the input receiving element and the driven plate arerelatively rotated. The window in the driven plate supports the elasticelement which expands or contracts due to the torsional vibration. Whenthe window is small in thickness, a greater bearing pressure is appliedto the window, and an edge of the window has its lifetime shortened.Thus, a plurality of disk-like sheet metal plates or thick casting partsmay be used to thicken and reinforce the driven plate.

Disadvantages of the prior art damper are listed below:

1) Since the hub flange and the driven plate are separately made, thereare a large number of parts making the overall configuration complicatedand costly to manufacture. Moreover, the flange of the boss extendsoutward to support the bearing. The boss itself, as a whole, is bulky.Since the boss is made of casting material, it has considerable mass andweight and is costly to manufacture.

2) The boss in the power output element protrudes toward thetransmission. Thus, the damper is large in an axial direction.

3) A seal element must be provided between the hub flange and otherparts to seal the fluid space. The number of components increasesbecause of the seal element making the device costly to manufacture.

4) The hub flange is supported by the bearing on an outer circumferenceof the boss in the power input element so as to rotate relative to thepower input element. The bearing is affected by thrust load and radialload. Thus, the bearing employed herein must be sufficiently large inthe radial direction. With such a large bearing, manufacturing iscostly, and the bearing occupies a large space in the radial directions.Consequently, a restriction is imposed upon a design of the inside ofthe dampening element.

5) The driven plate has an undesirably large mass and weight increasingcost and adding weight to the machine it is mounted in. In the case anautomobile, where weight reduces fuel efficiency, this is undesirable.

SUMMARY OF THE INVENTION

One object of the present invention is to reduce the number of parts ina power transmitting devices.

Another object of the present invention is to miniaturize a bearingbetween, for instance, a first and second flywheel in a two flywheelconstruction.

Another object of the present invention is to omit a bearing entirely.

It is further another object of the present invention to facilitateattachment of the bearing.

It is still another object of the present invention to reduce afabrication cost.

It is another object of the present invention to design the inside of adampening element with fewer design restrictions.

It is further another object of the present invention to position partsas concentric as possible with respect to one another.

It is still another object of the present invention to simplify aconfiguration of a power transmitting device.

It is yet another object of the present invention to absorb bendingvibration from a power input element and increase the total moment ofinertia.

It is still another object of the present invention to increase momentof inertia of a power output element in a damper.

It is another object of the present invention to reduce a weight of aboss.

It is further another object of the present invention to decreasedimensions of a damper in an axial direction.

It is still another object of the present invention to facilitatefabrication of a power transmission device.

It is yet another object of the present invention to reduce a weight ofa driven plate.

In one aspect of the present invention, a power coupling mechanismdisposed between the crankshaft of a rotary power producing device and atransmission includes at least a first power input plate connectable tothe crankshaft of a rotary power producing device, a dampening mechanismcoupled to the first power input plate and a driven plate coupled to thedampening mechanism. The dampening mechanism includes an annular housingformed with at least one axially extending annular protrusion. Thedriven plate is formed with at least one annular groove engaging andinterfitting with the annular protrusion such that engagement Betweenthe annular protrusion and the annular groove confines the driven plateagainst axial movement with respect to the first power input plate andprovides structural support against thrust and radial forces experiencedby the power coupling mechanism.

In another aspect of the invention, the housing is formed with twoopposing annular protrusions, both of the opposing annular protrusionsextending in axial directions toward one another. The driven plate isformed with two annular grooves, each of the grooves on opposite axialfaces thereof, the annular protrusions extending into the groovesradially and axially confining the driven plate with respect to thehousing and the first power input plate, thus allowing relative rotationof the driven plate with respect to the housing and the first powerinput plate.

In another aspect of the invention, a second power input plate iscoupled to the first power input plate, the two plates defining a fluidfilled chamber therebetween, the housing disposed within the fluidfilled chamber.

In another aspect of power coupling mechanism an annular metallic sealis fixed to the driven plate and biased to engage the second power inputplate to seal the fluid filled chamber.

At least one cup-like slider is slidably disposed within the housing,the driven plate being formed with at least one radially extendingprotrusion which extends into the cup-like slider, the slider definingtwo large cells within the housing and the protrusion defining two smallcells within the cup-like slider, the housing and the large and smallcells filled with viscous fluid such that fluid flows between adjacentcells in response to relative rotary displacement of the driven platewith respect to the housing.

In another aspect of the invention, a flexible disk-like plate having acenter hole and a plurality of bolt holes radially spaced apart from oneanother, defining a pitch circle, is boltable to the crankshaft of arotary power producing device via the bolt holes. A center hub iscoupled to and supports the first power input plate, the center hubextending through the center hole. A bearing within the power couplingmechanism has inner and outer races, the inner race mounted on thecenter hub, the driven plate rigidly coupled to the outer race, thebearing having a diameter smaller than the pitch circle.

In one embodiment of the present invention, a flywheel is disposed onthe bearing, the driven plate is connected to the flywheel, the flywheelhaving a friction surface. A clutch disk disposed adjacent to thefriction surface and a clutch coupler is connected to the flywheelincluding a pressure plate for selectively pressing the clutch diskagainst the friction surface and an elastic element supported by aportion of the flywheel for urging the pressure plate to the frictionsurface. Further, a ring gear is rigidly attached to the flexibledisk-like plate.

In another embodiment of the invention, a flexible disk-like platehaving a center hole and a plurality of bolt holes radially spaced apartfrom one another, defining a pitch circle, is boltable to the crankshaftof a rotary power producing device via the bolt holes. A hub is disposedradially inward of the driven plate, and at least partially extendsthrough the center hole. A center hole is formed in the first powerinput plate, the hub engaging both the flexible disk-like plate and thefirst power input plate for rotation therewith. A bearing having aninner and outer race, is configured such that the inner race issupported on a portion of the hub, the driven plate rigidly supported onthe outer race, the bearing having a diameter smaller than the pitchcircle. An inertia element is rigidly connected to the driven plate anda ring gear is rigidly connected to the inertia element.

In another embodiment of the invention, a flexible disk-like platehaving a center hole and a plurality of bolt holes radially spaced apartfrom one another, defining a pitch circle, is boltable to the crankshaftof a rotary power producing device via the bolt holes. A center hubcentrally disposed within the power coupling, is coupled to and supportsthe driven plate. A bearing within the power coupler has inner and outerraces, where the inner race mounted on a portion of the center hub, theouter race coupled to and supporting the first power input plate, thebearing having a diameter smaller than the pitch circle. The first powerinput plate is formed with a radially inwardly and axially extendingflange which extends partially through the center hole. An inertiaelement rigidly attached to the driven plate and a ring gear welded tothe inertia element.

A power relay device in an aspect of the present invention is a deviceprovided between a power input rotating element in an engine and a poweroutput rotating element in a transmission to transmit torque, and it hasa power input element, a flywheel, a dampening element a clutch diskassembly, and a clutch coupler. The dampening element elasticallyconnects the power input element and the flywheel in a circulardirection and dampens torsional vibration between the input element andthe flywheel. The clutch disk assembly has a clutch disk brought incontact with the friction surface of the flywheel and is connected tothe power output rotating element. The clutch coupler has a pressureplate for pressing the clutch disk against the friction surface and anelastic element held by the supporting element for urging the pressureplate against the friction surface of the flywheel.

In this power relay device, the torque, when applied from the powerinput rotating element in the engine to the power input element istransmitted through the dampening element to the flywheel. When thetorsional vibration is transmitted to the power input element, the powerinput element in the flywheel repeats torsional motions, during whichthe dampening element dampens the torsional vibration. In such asituation, when the pressure plate urged by the elastic element causesthe clutch disk of the clutch disk assembly to press against thefriction surface of the flywheel, the torque of the flywheel istransmitted via the clutch disk assembly to the power output rotatingelement in the transmission.

The flywheel assembly and the clutch are integrally assembled.Specifically, the elastic element of the clutch coupling mechanism isheld by the supporter of the flywheel, and a clutch cover as used in theprior art is omitted. This brings about decrease of parts in number.

A damper in another aspect of the present invention is a device fortransmitting torque between a power input rotating element and a poweroutput rotating element, and it includes a rotating element, a hubflange and a dampening element. The rotating element is connected to oneof the power input and output rotating elements. The hub flange has aboss coupled to the other of the power input and output rotatingelements and a flange formed integral with the boss at its outercircumference. The dampening element elastically connects the rotatingelement and the flange in a circular direction to dampen torsionalvibration between the rotating element and the hub flange.

In such a damper, receiving the torque from the power input rotatingelement allows it to be transmitted to the rotating element, the hubflange and the dampening element and the torque is applied to the poweroutput rotating element. When the torsional vibration is transmittedfrom the power input rotating element to the damper, the rotatingelement and the hub flange reciprocally perform torsional motions withthe dampening element interposed between them to dampen the torsionalvibration. Since the flange of the hub flange is formed integral withthe boss at its outer circumference, a driven plate as used in the priorart can be omitted, and a configuration of the damper can be simplified.This leads to a cost reduction.

A damper in still another aspect of the present invention is a deviceinterposed between an power input rotating element and a power outputrotating element for transmitting torque, and it has a first disk-likeelement, a second disk-like element, a rotating element, a bearing, adampening element and a seal element. The first disk-like element isconnected to one of the power input and output rotating elements. Thesecond disk-like element has its outer circumferential portion coupledto the first disk-like element and both the first and second disk-likeelement define a fluid space which is filled with fluid. The poweroutput element is coupled to the other of the power input and outputrotating elements. The bearing is interposed between the first disk-likeelement and the rotating element to support the first disk-like elementand the rotating element for relative rotations with each other. Thedampening element is placed in the fluid space and elastically couplesthe first disk-like element and the power output element in a circulardirection to dampen torsional vibration between them. The seal elementis interposed between the second disk-like element and the rotatingelement and urges the second disk-like element and the power outputelement repellently to each other to seal the fluid space and applypre-load to the bearing.

In such a damper, when the torque is received from the power inputrotating element, the first disk-like element, the dampening element andthe rotating element transmit the torque in this order to apply it tothe power output rotating element. When the damper receives torsionalvibration from the power input rotating element, the first disk-likeelement and the rotating element repeats reciprocal torsional motionswith the dampening element interposed between them to dampen thetorsional vibration therebetween.

In such a damper, the seal element urges the second disk-like elementand the rotating element repellently to each other to seal the fluidspace and apply pro-load to the bearing. Thus, with a single elementhaving two functions, parts can be reduced in number.

A damper in further another aspect of the present invention is a deviceplaced between a power input rotating element and a power outputrotating element to transmit torque, and it has a flexible plate, apower input element, a power output element, a dampening element and aninertia element. The flexible plate is coupled to the power inputrotating element and capable of flexing in its flexural direction. Thepower input element is foxed to the flexible plate while the poweroutput element is coupled to the power output rotating element. Thedampening element elastically couples the power input element and theoutput element in a circular direction to dampen torsional vibrationbetween the power input element and the power output element. Theinertia element is fixed to the flexible plate.

In such a damper, when the flexible plate receives the torque from thepower input rotating element, the power input element and the dampeningelement transmits it to the power output element. The torque from thepower output element is applied to the power output rotating element.The torsional vibration transmitted from the power input rotatingelement is dampened by the dampening element while flexural vibration isabsorbed by the flexible plate. In addition to that, since the inertialelement is fixed to the flexible plate, the total moment of inertia isincreased. Consequently, variations in torque from the engine can besufficiently absorbed.

A damper in yet another aspect of the present invention is a deviceinterposed between a power input rotating element and a power outputrotating element to transmit torque, and it has a disk-like flexibleplate, a power output element, a bearing and a dampening element. Thedisk-like flexible plate has a center hole, has its innercircumferential edge fixed to the power input rotating element, and iscapable of flexing in a flexural direction. The power output element hasa disk-like power input plate having its outer circumferential end fixedto an outer circumferential end of the flexible plate and having at itscenter a boss fitted in the center hole of the flexible plate, a poweroutput element coupled to the power out-put rotating element and abearing attached to the boss and supporting the power output element forrelative rotations with the power input plate in a circular direction.The dampening element elastically couples the power input element andthe power output element in a circular direction to dampen torsionalvibration between the power input element and the power output element.

In such a damper, the torque, when transmitted from the power inputrotating element is transmitted via the disk-like power input plate tothe dampening element and then applied from the dampening element viathe power output element to the power output rotating element. Flexuralvibration from the engine is absorbed by the disk-like flexible platewhile torsional vibration is dampened by the dampening element. In thiscase, the disk-like power input plate has a boss fitted in a center holeof the flexible plate and holds the bearing. Thus, the flexible plate,the boss, the bearing and the power output element are positioned moreconcentric with one another.

A damper in another aspect of the present invention is a deviceinterposed between a power input rotating element and a power outputrotating element to transmit torque, and it has a power input element, apower output element a dampening element and a ring gear to start anengine. The power input element is coupled to the power input rotatingelement while the power output element, which is rotatable relative tothe power input element, is coupled to the power output rotatingelement. When the torsional vibration is transmitted from the powerinput rotating element to the damper, the rotating element and the bossrepeat reciprocal torsional motions with the dampening elementinterposed between them to dampen the torsional vibration therebetween.

In such a damper, the disk-like element fixed to an output circumferenceof the boss is supported by the bearing. Thus, it is needless providinga portion in the boss which is supported by the bearing, and the bosscan be lightened. This brings about a cost reduction.

A damper in still another aspect of the present invention is a deviceinterposed between a power input rotating element and a power outputrotating element to transmit torque, and it has a first disk-likeelement, a second disk-like element, a rotating element and a dampeningelement. The first disk-like element is coupled to one of the powerinput rotating element and the power output rotating element. The seconddisk-like element has its outer circumference coupled to the firstdisk-like element, and the first and second disk-like elements togetherdefine a fluid space which is fined with fluid. The rotating element iscoupled to the other of the power input and output rotating elements.The dampening element is provided in the fluid space and elasticallycouples the first disk-like element and the rotating element in acircular direction to dampen torsional vibration between them. Pressurecaused in the fluid space allows an inner circumference of the seconddisk-like element to come in touch with the rotating element to seal thefluid space.

In such a damper, the torque of the power input rotating element istransmitted via the first disk-like element, the dampening element andthe rotating element to the power output rotating element. Whentorsional vibration is transmitted from the power input rotating elementto the damper, the first disk-like element and the rotating elementrepeat reciprocal torsional motions with the dampening elementinterposed between them to dampen the torsional vibration therebetween.In the damper, the pressure caused in the fluid space permits thecircumferential portion of the second disk-like element to come in touchwith the rotating element to seal the fluid space. Thus, a seal elementas used in the prior art can be omitted herein. This leads to a decreasein the number of parts and a cost reduction.

A damper in yet another aspect of the present invention is a device totransmit torque between a crankshaft in an engine and a power outputrotating element, and it has a disk-like flexible plate, a power inputelement, a power output element, a bearing and a dampening element. Thedisk-like flexible plate has its inner circumferential edge fixed to atip of the crankshaft by a plurality of fixing elements. The power inputelement is fixed to an outer circumferential edge of the flexible plate.The power output element is coupled to the power output rotatingelement. The bearing is positioned inside a pitch circle of the fixingelements and holds the power input element and the power output elementfor relative rotations with each other. The dampening elementelastically couples the power input element and the power output elementin a circular direction to dampen torsional vibration between the powerinput element and the power output element.

In such a damper, when the torque is received from the crankshaft in theengine, the disk-like flexible plate, the power input element, thedampening element and the power output element transmit the torque inthis order to apply it to the power output rotating element. Flexuralvibration from the engine is absorbed by the disk-like flexible platewhile the torsional vibration is dampened by the dampening element.Herein, since the bearing is positioned inside the pitch circle of thefixing elements, the inside of the dampening element can be designedwith less restriction.

The power input element consists of a disk-like element having its outercircumferential edge coupled to the flexible plate at its outercircumferential edge, and a boss fixed to an inner circumferential edgeof the disk-like element and having its outer circumference fitted inthe bearing, and the flexible plate has a center hole. Preferably, theboss is fitted in the center hole for support.

In such a damper, since the power input element has its boss fitted inthe center hole of the flexible plate, parts are disposed more eccentricwith one another.

A damper in another aspect of the present invention is a device totransmit torque between a power input rotating element in an engine anda power output shaft in a transmission, and it has a sheet metaldisk-like plate, a hub and a dampening element. The sheet metaldisk-like plate includes a disk element coupled to the power inputrotating element, and a center cap protruding toward the engine. The hubhas a boss received in a center cap in the disk-like plate and connectedto the power output shaft, and a flange spreading outward from the boss.The dampening element elastically couples the disk-like plate and theflange in a circular direction to dampen torsional vibration between thedisk-like plate and the hub.

In such a damper, when the torque is transmitted from the power inputrotating element the sheet metal disk-like plate, the dampening elementand the hub transmit the torque to apply it to the power output shaft.When the torsional vibration is transmitted from the power inputrotating element to the damper, the sheet metal disk-like plate and thehub repeat reciprocal torsional motions with the dampening elementinterposed between them to dampen the torsional vibration therebetween.In this damper, since the boss of the hub is housed in the center cap ofthe sheet metal disk-like plate, an axial dimension of the damper isreduced.

A damper in still another aspect of the present invention is a deviceinterposed between a power input rotating element and a power outputrotating element to transmit torque, and it has a power input element, apower output element and a dampening element. The power input element iscoupled to the power input rotating element while the power outputelement, which is rotatable relative to the power input element, iscoupled to the power output rotating element. The dampening elementincludes an elastic element coupling the power input element and thepower output element in a circular direction, and a resistance generatorfor generating resistance during relative rotations by the power inputand output elements, and it supports the power input and output elementsrotatable relative to each other in a circular direction and receives atleast part of load caused between the power input and output elements.

In such a damper, when the torque is received from the power inputrotating element, the power input element, the dampening element theelastic element and the power output element transmit the torque toapply it to the power output rotating element. When torsional vibrationis transmitted from the power input rotating element to the damper, thepower input element and the power output element perform reciprocaltorsional motions with the elastic element interposed between them.Simultaneously, the resistance generator generates the resistance todampen the torsional vibration. In this damper, since the dampeningelement supports the power input and output elements rotatably relativeto each other and receives at least part of the load caused betweenthem, a bearing, if provided between the power input and outputelements, can be downsized. As the bearing becomes smaller indimensions, a cost decreases.

A damper in yet another aspect of the present invention is a device totransmit torque between a power input rotating element and a poweroutput rotating element, and it has a rotating element, a single sheetmetal disk-like plate, and a dampening element. The rotating element iscoupled to one of the power input and output rotating elements. Thesheet metal disk-like plate is coupled to the other of the power inputand output rotating elements, and it has a window hole extending in acircular direction and a flap surrounding the window hole. The dampeningelement is supported by the flap within the window hole, and it has anelastic element coupling the rotating element and the disk-like plate ina circular direction, and a resistance generator generating resistanceduring relative rotations by the rotating element and the disk-likeplate.

In such a damper, the rotating element, the dampening element and thesheet metal disk-like plate transmit the torque from the power inputrotating element to the power output rotating element. When torsionalvibration is transmitted from the power input rotating element to thedamper, the rotating element and the sheet metal disk-like plate repeatsreciprocal torsional motions with the dampening element interposedbetween them to dampen the torsional vibration therebetween.

In this damper, the sheet metal disk-like plate is provided with theflap surrounding the window hole, and the flap supports the elasticelement of the dampening element. Thus, with that flap, bearing stressimposed upon a portion at which the elastic element of the disk-likeplate is supported is reduced. Specifically, durability required on thesingle sheet metal disk-like plate can be assured, and this, in turn,leads to lightening the device and reducing a cost.

These and other objects, features, aspects and advantages of the presentinvention will become more fully apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings where like reference numerals denote correspondingparts throughout, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, side section showing a power transfer apparatusin accordance with a first embodiment of the present invention;

FIG. 2 is a part section, part elevation rear view (as viewed from thetransmission) of the power transfer apparatus depicted in FIG. 1;

FIG. 3 is a fragmentary, part section, part elevation, front view,showing further details of the power transfer apparatus depicted in FIG.1, as seen from the engine;

FIG. 4 is a fragmentary, enlarged view of a portion of FIG. 1, on aslightly enlarged scale;

FIG. 5 is a fragmentary, enlarged view of a portion of FIG. 2, showingno relative displacement of several parts of the power transferapparatus (no torsional stress);

FIG. 6 is a fragmentary, enlarged view of a portion of FIG. 2, similarto FIG. 5, showing relative displacement of several parts of the powertransfer apparatus due to torsional stress on the apparatus;

FIG. 7 is a fragmentary, enlarged view of a portion of FIG. 2, similarto FIGS. 5 and 6, showing further relative displacement of several partsof the power transfer apparatus due to torsional stress on theapparatus;

FIG. 8 is a fragmentary, enlarged view of a portion of FIG. 2, similarto FIGS. 5, 6 and 7, showing still further relative displacement ofseveral parts of the power transfer apparatus due to torsional stress onthe apparatus;

FIG. 9 is a fragmentary section of a portion of FIG. 2, on a slightlyenlarged scale, showing the apparatus in a torsion free state withgenerally no relative displacement between parts of the apparatus;

FIG. 10 is a fragmentary section of a portion of FIG. 2, similar to FIG.9, showing relative displacement of several parts of the power transferapparatus due to torsional stress on the apparatus;

FIG. 11 is a fragmentary, side section, showing a power transferapparatus in accordance with a second embodiment of the presentinvention;

FIG. 12 is a fragmentary, part section, part elevation rear view of theapparatus depicted in FIG. 11, as seen from the transmission;

FIG. 13 is a fragmentary, part section, part elevation front view of theapparatus depicted in FIG. 11, as seen from the engine;

FIG. 14 is a fragmentary section of a portion of FIG. 11, on a slightlyenlarged scale;

FIG. 15 is a fragmentary section of a portion of FIG. 12, on a slightlyenlarged scale, showing no relative displacement of several parts of thepower transfer apparatus (no torsional stress);

FIG. 16 is a fragmentary, enlarged view of a portion of FIG. 12, similarto FIG. 15, showing relative displacement of several parts of the powertransfer apparatus due to torsional stress on the apparatus;

FIG. 17 is a fragmentary, enlarged view of a portion of FIG. 12, similarto FIGS. 15 and 16, showing further relative displacement of severalparts of the power transfer apparatus due to torsional stress on theapparatus;

FIG. 18 is a fragmentary, enlarged view of a portion of FIG. 12, similarto FIGS. 15, 16 and 17, showing still further relative displacement ofseveral parts of the power transfer apparatus due to torsional stress onthe apparatus;

FIG. 19 is a fragmentary section of a portion of FIG. 12, showingrelative displacement of several parts of the power transfer apparatusdue to torsional stress on the apparatus;;

FIG. 20 is a fragmentary, side section schematic diagram showing a powertransfer apparatus in accordance with a third embodiment of the presentinvention;

FIG. 21 is a fragmentary, side section schematic diagram showing a powertransfer apparatus in accordance with a fourth embodiment the presentinvention;

FIG. 22 is a fragmentary, side section schematic diagram showing a powertransfer apparatus in accordance with a fifth embodiment of the presentinvention;

FIG. 23 is a fragmentary, side section schematic diagram showing a powertransfer apparatus in accordance with a sixth embodiment the presentinvention;

FIG. 24 is a fragmentary section, rear view of a portion of theapparatus depicted in FIG. 23, on a slightly reduced scale;

FIG. 25 is a fragmentary section taken along the line II--II in FIG. 24,on a slightly enlarged scale;

FIG. 26 is a fragmentary section taken vertically from the point IV inFIG. 25, on a slightly enlarged scale; and

FIG. 27 is a fragmentary section taken vertically from the point V inFIG. 25, on a slightly enlarged scale.

DESCRIPTION OF THE PREFERRED EMBODIMENT First Embodiment

FIGS. 1 to 10 illustrates a power transfer device 201 in accordance witha first embodiment of the present invention. The power transfer device201 works to transmit torque from a crankshaft 301 in an engine to amain drive shaft 302 in a transmission. In FIG. 1, the engine (notshown) is positioned on the left in the figure while the transmission(not shown) is positioned on the right in the figure. Line O--O in FIG.1 is a rotation axis of the power transfer device 201, and R1 denotes adirection of rotations by the power transfer device 201.

The power transfer device 201 is includes a flywheel assembly 1, aclutch disk assembly 202 and a clutch coupler 203 all integrally fixedto one another.

The flywheel assembly 1 primarily includes a flexible plate 2, a ringelement 8 fixed to the flexible plate 2, a disk-like flywheel 3, and adampening element 4 elastically coupling the ring element 8 and theflywheel 3 in a circular direction to dampen torsional vibration betweenthem.

The flexible plate 2 is a roughly disk-shaped component which can flexslightly in axial directions and which has a greater rigidity in arotational direction. As is shown in FIGS. 1 and 2, the flexible plate 2has a center hole 2a at its center. The flexible plate 2 has a pluralityof round holes 2b (see FIG. 3) formed at spaced apart intervals in acircular direction at a radially intermediate portion of the plate 2.Inward from the round holes 2b a plurality of bolt holes 2c arecircularly formed on the plate 2. Bolts 6 fitted through the bolt holes2c fix an inner circumferential edge of the flexible plate 2 to an endof the crankshaft 301. As is shown in FIG. 3, a plurality of archedinertia elements 7 are fixed to the flexible plate 2 by rivets 51. Theinertia elements 7 causes moment of inertia of the flywheel assembly 1to increase. Since the inertia elements 7 are arcuate in shape and aresegmented, the inertia elements 7 do not restrain or prevent theflexible plate 2 from flexing itself in axial directions. An outercircumferential edge of the flexible plate 2 is fixed to the ringelement 8 by bolts 10, with the disk plate 9 interposed between them.The inertia elements 7 have notches corresponding to the bolts 10,respectively.

A ring gear 11, used to start the engine, is fixed to the outercircumference of the ring element 8.

The dampening element 4 has a first power input plate 13, a second powerinput plate 14, a boss 15, a driven plate 19, a coil spring 22 and aviscous resistance generator 25. The first power input plate 13 and thesecond power input plate 14 are disk-like plate elements. An outercircumferential wall fixed to an outer circumferential edge of the firstpower input plate 13 is formed at an outer circumference of the secondpower input plate 14, extending toward the engine. The outercircumferential wall is welded to an inner circumference of the ringelement 8. The inner circumferential edge of the second power inputplate 14 is larger in diameter than that of the first power input plate13. The first power input plate 13 and the second power input plate 14together define a fluid space A for accommodating the driven plate 19,the coil spring 22, the viscous resistance generator 25 and the like.The space A is filled with viscous fluid.

The driven plate 19, which is a disk-shaped element has its innercircumferential edge coupled to the flywheel 3 by rivets 20. A pluralityof window holes 19a are formed at a radially intermediate portion of thedriven plate 19, respectively extending in a circular direction. Annulargrooves 19b (see FIGS. 1 and 2) for sealing are formed at opposite sidesnear an outer circumferential edge of the driven plate 19. A pluralityof projections 19d extend outward from a circumferential surface 19c ofthe driven plate 19 in a radial direction.

The coil springs 22 are placed within the window holes 19a in the drivenplate 19. Sheet elements 23 are provided at opposite ends of the coilspring 22. The first power input plate 13 and the second power inputplate 14 respectively have spring receptacles 13a and 14a in a positioncorresponding to the window hole 19a of the driven plate 19. The seatelements 23 contact opposite ends of the spring receptacles 13a and 14ain a circular direction. Thus, the power input plates 13 and 14 and thedriven plate 19 are elastically coupled in a circular direction with thecoil spring 22 interposed between them. The seat element 23, under anidle state as shown in FIG. 2, has its circumference only partially putin contact with the spring receptacles 13a and 14a of the power inputplates 13 and 14 and the window hole 19a of the driven plate 19 at theirrespective ends. In other words, the coil spring 22 is accommodated intorsional contact within the window hole 19a.

The viscous resistance generator 25 will now be described,

The viscous resistance generator 25 is comprised of an annular housing27 provided at an outermost circumference within the space A, aplurality of pins 28 coupling the housing 27 to the first and secondpower input plates 13 and 14, and a plurality of slide stoppers 27aformed within the housing 27, the pins 28 extending through the slidestoppers 27a.

The annular housing 27 is placed inside an outer circumferential wall ofthe second power input plate 14 and has its opposite end surfaces in anaxial direction interposed between the power input plates 13 and 14.Within the annular housing 27, there is provided an annular fluidchamber B which is filled with viscous fluid. Within the annular housing27, the plurality of stoppers 27a divide the annular fluid chamber Binto a plurality of arched fluid sub-chambers B1. The pin 28 allows theannular housing 27 to revolve integral with the first and second powerinput plates 13 and 14. A width of the annular housing 27 whichdetermines viscous resistance depends upon a length of a shank of thepin 28. The annular housing 27 is provided with two opposing annularprojections 27b which protrude inwardly at inner ends of the annularhousing 27, the projections 27b defining an opening 27e (FIG. 1) and theprojections 27b are fitted in the annular grooves 19b formed in thedriven plate 19 to seal an inner opening of the annular fluid chamber B.The projection 27b is an engagement portion fitted in the annulargrooves 19b formed in the driven plate 19 partakes of load (thrust load,radial load and bending load) caused between a power input system (thefirst and second power input plates 13 and 14 and the housing 27) and apower output system (the driven plate 19 and the flywheel 3) with theviscous fluid intervening therebetween. The engagement portion and abearing 17 (described below) provide support between both the input andoutput systems. Thus, the seal of the annular fluid chamber B also worksas a supporter of the load, and this brings about a cost reduction.

Return holes 27c are formed in inner opposite end surfaces ofintermediate portions of the housing 27, between the stoppers 27a. Thereturn holes 27c permit the viscous fluid to move between the annularfluid chamber B and the inner space A without interruption, as will beexplained in greater detail below.

The projections 19d of the driven plate 19 correspond in position to theintermediate portions between the stoppers 27a, and in a torsion freestate, are positioned adjacent to the return holes 27c, as shown in FIG.2.

Within the arched fluid chamber B1, a plurality of cap-like slider 29are disposed such that the cap-like structure of each slider 29 coversone of the projections 19d of the driven plate 19, as is shown in FIGS.2, and 5-10. The slider 29 has a curved outer surface fitted in an innercircumference of the annular housing 27, and is slidably disposed formovement in a circular direction within the arched fluid chamber B1. Theslider 29 is movable in the circular direction in a range where walls inradial directions stop the projection 19d of the driven plate 19. Legs29a expands radially inward from four interior comers at an innercircumference of the slider 29, and tips of the legs 29a are in contactwith annular projections 27b such that the sliders 29 are confinedwithin the annular housing 27.

Each of the arched fluid sub-chambers B1 is further divided into a firstlarger cell 31 in a R2 direction (see FIG. 2) and a second larger cell32 in an R1 direction by the slider 29. The interior of the slider 29 isdivided into a first smaller cell 33 in the R2 direction and a secondsmaller cell 34 in the R1 direction by the projection 19d of the drivenplate 19. As shown in FIGS. 5 and 6, a gap defined between theprojection 19d of the driven plate 19 and the slider 29 and the returnhole 27c permit the viscous fluid to move from the first smaller cell 33to the second smaller cell 34 and vice versa. The gap around the leg 29aof the slider 29 in the R2 direction also permits the viscous fluid tomove between the first larger cell 31 and the first smaller cell 33while gap around the leg 29a of the slider 29 in the R1 directionpermits the viscous fluid to move between the second smaller cell 34 andthe second larger cell 32. When a wall of the slider 29 comes intocontact with the projection 19d, however, the viscous fluid is blockedbetween the inside and outside of the slider 29.

A choke C (see FIGS. 2, 9 and 10) is provided between an innercircumferential surface of the stopper 27a and an outer circumferentialsurface 19c of the driven plate 19. When the viscous fluid passes thechoke C, a large viscous resistance is created.

An inner circumference of the driven plate 19 and the second flywheel 3are fixed to each other by the rivets 20 with a spring seal 35sandwiched between them, as shown in FIG. 4. The spring seal 35 is anannular ring of thin sheet metal and includes a fixed portion 35a havinga plurality of holes through which the rivets 20 are fitted, an outercylindrical portion 35b extending from the fixed portion 35a toward thetransmission, and a resilient portion 35c spreading outward from anouter cylindrical portion 35b. The resilient portion 35c is in contactwith an inner circumferential end of the second power input plate 14 ona side close to the engine to urge it toward the transmission. Thespring seal 35 seals the fluid space A between the second power inputplate 14 and the flywheel 3.

The center hole in the inner circumferential end of the first powerinput plate 13 is fitted on the boss 15 and fixed by, for instance,welding, as shown in FIG. 1. An outer circumferential surface 15a of theboss 15 close to the engine is fitted in the center hole 2a of theflexible plate 2. The boss 15 is provided with a center hole 15cextending through in an axial direction and a hole 15b extending in aradial direction to lead to the center hole 15c and the fluid space A. Arivet 16 is fitted through the center hole 15c. In assembling thedevice, the center hole 15c and the hole 15b are utilized to fill thefluid space A with the viscous fluid.

The bearing 17 is placed between an outer circumferential surface of theboss 15 close to the transmission and an inner circumference of the flywheel 3, and it holds the flywheel 3 rotatably relative to the boss 15.An inner race of the bearing 17 is fixed to the boss 15 by a groove inthe boss and a head of the rivet 16. Thus, the bearing 17 as well as theboss 15 is put in position by the center hole 2a of the flexible plate2. Thus, the flexible plate 2, the boss 15 and the bearing 17 arearranged to each other concentrically.

Since engagement of the annular projection 27b of the housing 27 and thegrooves 19 of the driven plate 19 in the viscous resistance generator 25partakes of the thrust load and the radial load, the load imposed on thebearing 17 can be reduced. Thus, dimensions of the bearing can bereduced in a radial direction, and in this embodiment, for example, thebearing 17 is placed within a pitch circle D of the bolts 6 (see FIG.2). With the bearing 17 positioned within the pitch circle D of thebolts 6, the inside of the dampening element 4 can be designed with lessrestriction. Thus, it is possible to design the driven plate 19 suchthat it extends more inwardly than driven plates in the prior art.Similarly, the coil spring 22 may be provided more inwardly toward thecenter of the apparatus, as compared to the prior art

The bearing 17 has seal elements at its opposite ends to seal a gapbetween the inner race and an outer race. The seal elements tightly sealin lubricant between the inner race and the outer race and seal thefluid space A between the boss 15 and the inner circumference of theflywheel 3.

The flywheel 3 has a friction surface 3a close to the transmission.There lies a projection 3d at an outer circumference of the frictionsurface 3a, extending toward the transmission. The projection 3d extendscircumferencially, and is divided into three segments, as is indicatedin FIG. 2. As is shown in FIG. 1, on the inner circumference of theflywheel 3 has near its inner circumference, a radially inwardlyprojecting flange 3c is formed to engage the outer race of the bearing17 close to the engine.

The clutch disk assembly 202 includes a clutch disk 205 having frictionfacing on its opposite sides, an annular plate 206 having its outercircumferential end fixed to an inner circumferential end of the clutchdisk 205 by a rivet 206a, and a hub flange 207 having a flange 207afixed to an inner circumferential end of the annular plate 206 by aplurality of rivets 206b. In an inner circumference of the hub flange207, a spline hole 207b engaging a spline of a main drive shaft 302 isformed.

A clutch coupler 203 is primarily comprised of an annular pressure plate209 inside the projection 3d, and a diaphragm spring 210. The pressureplate 209 is coupled to the flywheel 3 with a strap plate 211 (FIG. 2)extending between them along a tangential line of a circumference. Thediaphragm spring 210 is, as is shown in FIG. 2, includes an annularpressing portion 210a and a plurality of levers 210b radially extendinginward from the pressing portion 210a. An outer circumferential end ofthe pressing portion 210a is supported at its side close to thetransmission by a snap ring 215 fixed to an inside of the projection 3dof the flywheel 3. A clutch cover as used in the prior art is omittedherein, and the number of parts is decreased. An inner circumferentialend of the pressing portion 210a urges the pressure plate 209 toward theengine. Tips of the levers 210b engage a release device 204.

The release device 204 includes a lever plate 218 contactable with thelevers 210b of the diaphragm spring 210, a release bearing 217 fixed toan inner circumference of the lever plate 218, a first cylindricalelement 219 to which an inner circumferential end of the release bearing217 attached, and a second cylindrical element 220 partially inserted inand fixed to the first cylindrical element 219. When the secondcylindrical element 220 is moved toward the transmission by a device notshown, the lever plate 218 pulls out the levers 210b of the diaphragmspring 210 toward the transmission to release the pressure plate 209from the pressing by the diaphragm spring 210.

An operation of the power transfer device will be described below.

When torque is applied from the crank shaft 301 to the flexible plate 2,the ring element 8, the first power input plate 13, the second powerinput plate 14 and the coil spring 22 transmit the torque to the drivenplate 19. The torque transmitted to the driven plate 19 is furthertransmitted to the flywheel 3 and the clutch disk assembly 202 and thento the main drive shaft 302. Flexural vibration transmitted from thecrank shaft 301 to the ring element 8 are suppressed by the flexibleplate 2 and generally do not easily reach the dampening element 4. Ifthe flexural vibration is transmitted thereto, the engagement of theannular projection 27b of the housing 27 with the grooves 19b of thedriven plate 19 partake in responding to the bending load. Thus, sincethe load imposed upon the bearing 17 is reduced, the bearing 17 can bedownsized in a radial direction.

When the release device 204 is shifted toward the transmission thepressure plate 209 is released from the pressing by the diaphragm spring210, and consequently, the clutch disk 205 leaves from the frictionsurface 3a of the flywheel 3. Although simultaneously release loadaffects the flywheel 3 to impose thrust load upon the bearing 17, theannular projection 27b of the annular housing 27 and the bearing 17partake the load applied to the flywheel 3 because the flywheel 3 isfixed by the driven plate 19 and the rivets 20. Thus, since the loadimposed upon the bearing 17 is reduced, the bearing 17 can be downsizedin a radial direction, and the cost reduced bearing can be obtained.

An operation of the flywheel assembly 1 when torsional vibration istransmitted from the crank shaft 301 to the flywheel assembly 1 will bedescribed. The operation in transmitting the torsional vibration willherein be described where a power input system (the first power inputplate 13, the second power input plate 14 and the annular housing 27)experiences torsional stress and where a power output system (the drivenplate 19 and the flywheel 3), fixed to other elements not shown, hasrotary power transmitted to it.

In the operation of the present invention, examples of both small andlarge torsional vibration will be discussed. First small levels oftorsional vibration are discussed. A small level of torsional vibrationtypically causes a small torsional angle of displacement (minutevibration) where the wall of the slider 29 in a circular direction doesnot come in contact with the projection 19d of the driven plate 19 istransmitted and that the annular housing 27, which is idle as shown inFIG. 5, is distorted toward the R2 direction. In such a situation, theslider 29 moves toward the R2 direction, and as shown in FIG. 6, thefirst smaller cell 33 expands within the slider 29 while the secondsmaller cell 34 contracts. The viscous fluid flowing from the secondsmaller cell 34 to the first smaller cell 33 passes between the outercircumference of the slider 29 and the projection 19d and through thereturn hole 27c. The viscous fluid passes the return hole 27c to movebetween the slider 29 and the annular space A with a small fluid flowresistance.

When the annular housing 27 is continuously displaced from a state asshown in FIG. 6, the wall extending along the circumference close to R1comes in contact with the projection 19d of the driven plate 19 in theslider 29, as shown in FIG. 7. After that the slider 29 engages thedriven plate 19, and the annular housing 27 and the slider 29 rotatesrelative to each other. Although the second larger cell 32 and thereturn hole 27c are conducted to each other in a state as shown in FIG.7, continuous distortion of the annular housing results in the returnhole 27c being stopped up by the projection 19d, as shown in FIG. 8. Asimilar operation occurs in the event that the annular housing 27 isdisplaced from an idle state as shown in FIG. 5 in the R1 direction.

Since the sliders 29 and the annular housing 27 do not rotate or are notdisplaced relative to each other under the minute vibration, the secondlarger cell 32 does not contract and the viscous fluid does not passthrough the choke C. This means a large viscous resistance does notarise under the minute vibration. The coil spring 22 expands andcontracts, torsionally contacts the window hole 19a of the driven plate19 and the spring receptacles 13a and 14a of the power input plates 13and 14; and thus the coil spring 22 exhibits a low rigidity.Specifically, under the minute vibration, characteristics of the lowrigidity and low viscous resistance can be attained, and they areeffective to suppress abnormal sound like clattering sound, heavy soundor the like.

An operation in transmitting torsional vibration of a large torsionalangle (referred to as `grand vibration` hereinafter) will now bedescribed.

It is now assumed that the annular housing 27, from a torsion freestate, as shown in FIG. 9, experiences torsion and is displaced relativeto the driven plate 19 in the R2 direction. Accordingly, the slider 29is shifted toward R2, and the displacements as are shown with respect tothe minute vibration as illustrated in FIGS. 5 to 8 are experienced.When the second larger cell 32 on the side of R2 is sealed because ofcontact between the slider 29 and the projection 19d of the driven plate19 as shown in FIG. 8, the second larger cell 32 begins to contract.This results in the viscous fluid in the second larger cell 32 passingthe choke C to flow into the arched fluid sub-chamber B1 on the side ofR1. When the viscous fluid flows through the choke C, a large viscousresistance is created. The viscous fluid passes the return hole 27c andsmoothly flows into the first larger cell 31.

When the housing 27 is displaced from the position shown in FIG. 10 inthe R1 direction, the slider 29 passes by a neutral position (shown inFIG. 9), and displacement reverse to that shown in FIG. 10 isexperienced.

As has been described, a large viscous resistance is experienced duringa grand vibration. In addition to that, the rigidity is enhanced becausea seat element 23 of the coil spring 22 contacts an end of the windowhole 19a and ends of the spring receptacles 13a and 14a as the torsionalangle becomes larger. Thus, under the grand vibration, characteristicsof a high rigidity and a large viscous resistance are obtained, and thiseffectively dampens vibration upon tip-in-tip-out (large vibrationforward and backward of an automobile caused by rapid operation of anaccelerating pedal).

It is assumed now that the minute vibration is transmitted under thecondition where the annular housing 27 is displaced in the R2 directionby a limited angle relative to the driven plate 19. The slider 29repeats reciprocal torsional motions relative to the projection 19d inan angular range where the wall in a circular direction of the slider 29is not in contact with the projection 19d. In such a situation, theviscous fluid does not flow at the choke C nor cause a large viscousresistance. Thus, even with such a condition that the annular housing 27and the driven plate 19 make a large torsional angle, the minutevibration can be effectively absorbed.

Second Embodiment

FIG. 11 to FIG. 19 show a damper 1' in second embodiment of the presentinvention. The damper 1' is a device to transmit torque from acrankshaft 301 in the engine to a main drive shaft 302 in atransmission. In FIG. 11, the engine (not shown) is positioned on theleft of the figure while the transmission (not shown) is positioned onthe right. Line 0--0 in FIG. 1 is a rotation axis line of the damper 1',and R1 in FIG. 2 denotes the direction of rotation of the damper 1'. R2denotes a direction of displacement of relatively moveable parts, aswill be more apparent in the following description.

The damper 1' includes many parts previously described in the firstembodiment although with some modifications, such as a flexible plate 2,a ring element 8 fixed to the flexible plate 2, a hub flange 3, and adampening element 4 elastically coupling the ring element 8 and the hubflange 3 in a circular direction to dampen torsional vibration betweenthem.

The flexible plate 2 is a roughly disk-like element which is capable offlexing in axial directions, but exhibits rigidity in its rotationdirection. The flexible plate 2 has a center hole 2a at its center. Theflexible plate 2 has a plurality of round holes 2b circularly formed atthe same intervals at its intermediate portion in a radial direction. Aplurality of bolt holes 2c are formed at the same intervals in acircular direction inward from the round holes 2b. A bolt 6 extendingthrough each bolt hole 2c fix the inner circumferential end of theflexible plate 2 to a tip of a crank shaft 101. To an outercircumference of the flexible plate 2 close to the engine, a pluralityof arched inertia elements 7 as shown in FIG. 13 are fixed by rivets 51.The inertial elements 7 causes moment of inertial of the damper 1 toincrease. Since the inertial elements are segmented annular elements,they do not prevent the flexible plate 2 from flexing itself in theflexural direction, An outer circumferential end of the flexible plate 2is fixed to the ring element 8 by a plurality of bolts 10, with adisk-like plate 9 interposed between them. The inertia elements 7respectively have notches corresponding to the bolts 10.

The hub flange 3 includes a boss 3a and a flange 3b integrally formed atan outer circumference of the boss 3a. At the center of the boss 3a, aspline hole 3c engages with spline teeth of the main drive shaft 302extending from the transmission. The flange 3b extends radiallyoutwardly to support a dampening element 4, described below.

The flange 3b of the hub flange 3 is provided with an inertial element42 close to the transmission. The inertial element 42 is a disk-likeelement covering a second power input plate 14 close to thetransmission, and its inner circumferential end is fixed to the flange3b and the driven plate 19 by rivets 20. With the inertia element 42,moment of inertia of a power output system is increased. Moreover, aring gear 11 is welded to an outer circumference of the inertia element42 by welds W. Although the ring gear 11 as used in the prior art is anelement welded to the outer circumference of the an element such as aflexible plate (similar to plate 2), it is shifted from a power inputsystem to the power output system to easily increase the moment ofinertia of the power output system in this embodiment. When the momentof inertia of the power output system is increased, it is possible todecrease a resonance frequency down to an idling speed (a practicalnumber of revolutions) or below. Since the ring gear 11 is used toincrease the moment of inertia of the inertia element 42, it is notnecessary to include extra weights or the like on the inertia element,and this leads to a cost reduction.

The damper 1' includes a first power input plate 13, a second powerinput plate 14, a driven plate 19, a coil spring 22 and a viscousresistance generator 25.

The first power input plate 13 and the second power input plate 14 aresheet metal disk-like elements. An inner circumferential end of thefirst power input plate 13 extends inward in a radial direction beyondan inner circumferential end of the second power input plate 14. Thesecond power input plate 14 has its outer circumference provided with anouter circumferential wall which extends toward the engine and is fixedto an outer circumferential end of the first power input plate 13. Theouter circumferential wall is welded to an inner circumference of thering element 8. The first power input plate 13 and the second powerinput plate 14 define a fluid space A which accommodates the drivenplate 19, the coil spring 22, the viscous resistance generator 25 and soforth. The fluid space A is filled with viscous fluid.

At an intermediate portion of the plate 19 in a radial direction, aplurality of window holes 19a are formed, extending in a circulardirection. Annular grooves 19b for sealing are formed on oppositesurfaces of an outer circumferential end of the hub flange 3b. Aplurality of projections 19d protrude outward in a radial direction froman outer circumferential surface 19c of the hub flange 3b.

The coil spring 22 is made up with large and small coil springs placedin the window hole 19a of the hub flange 3b. Seat elements 23 arepositioned at opposite ends of the coil spring 22. The first power inputplate 13 and the second power input plate 14 respectively have springreceptacles 13a and 14a in a position corresponding to the window hole19a. Seat elements 23 are in contact with opposite ends of the springreceptacles 13a and 14a in a circular direction. Thus, the first andsecond power input plates 13 and 14 are elastically coupled in acircular direction to the output plate 19 by the coil spring. In an idlestate as shown in FIG. 12, the seat elements 23 have only theirrespective inner circumferences put in contact with the ends of thespring receptacles 13a and 14a and the end of the window hole 19a. Inother words, the coil spring 22 is held in the window hole 19a and thespring receptacles 13a and 14a, being in torsional contact with them.

The viscous resistance generator 25 will now be described.

The viscous resistance generator 25 includes an annular housing 27placed at an outermost circumference within the fluid space A, aplurality of pins 28 coupling the annular housing 27 to the first andsecond power input plates 13 and 14, and a plurality of sliders 29 aredisposed in the housing 27.

The annular housing 27 is positioned inside an outer circumferentialwall of the second power input plate 14, having its opposite surfaces inan axial direction sandwiched by the power input plates 13 and 14. Anopening 27e extending in a circular direction is formed in an innercircumference of the annular housing 27, and an outer circumference ofthe output plate 19 extends into the opening 27e. An annular fluidchamber B which is filled with viscous fluid is formed within theannular housing 27. A plurality of stoppers 27a are integrally formed atspaced apart intervals in a circular direction in the annular housing27. The stoppers 27a divide the annular fluid chamber B into a pluralityof arched fluid sub-chambers B1. The stopper 27a has a hole in which apin 28 is inserted, The pin 28 has its opposite ends engaged with thepower input plates 13 and 14 allowing the annular housing 27 and thepower input plates 13 and 14 to rotate as a unitary structure. A widthof the annular housing 27, which determines a viscous resistance,depends upon a length of a shank of the pin 28. The annular housing 27is provided with an annular opposing projections 27b (surrounding theopening 27e) which protrude inward at an inner end of the annularhousing 27, and the projections 27b are fitted in the annular grooves19b formed in the driven plate 19 to seal an inner opening of theannular fluid chamber B. The projections 27b are engagement portionsfitted in the annular grooves 19b and partake load (thrust load, radialload and bending load) caused between a power input system (the firstand second power input plates 13 and 14 and the housing 27) and a poweroutput system (the hub flange 3) with the viscous fluid interveningtherebetween.

Return holes 27c are formed in inner opposite end surfaces ofintermediate portions between the stoppers 27a, and the return holes 27cpermit the viscous fluid to move between the annular fluid chamber B andthe inner space A without interruption.

The projections 19d of the hub flange 3b are positioned adjacent to thereturn holes 27c, when the damper 1 is in a torsion free or idle stateas shown in FIG. 12.

Within the arched fluid sub-chamber B1, a cap-like slider 29 is disposedwhich covers the projections 19d of the plate 19. The slider 29 has anouter circumferencial surface which slidably contacts an innercircumferencial surface of the annular housing 27, and is slidable in aradial direction within the arcuate fluid chamber B1. The movement ofthe slider 29 confined by the projections 19d. The slider 29 is formedwith notches 29a at the opposite end walls on an inner circumference.Additionally, notches 29b are formed at opposite walls of the slider 29in an axial direction and the inner circumference in a radial direction.Movement of the slider 29 is further confined by stopper 27a. The slider29 is further confined within the chamber B1 by the annular projections27b of the annular housing 27.

The slider 29 divides each of the arched fluid chambers B1 into a firstlarger cell 31 in the R2 direction and a second larger cell 32 in the R1direction. The interior of the slider 29 is divided into a first smallercell 33 in the R2 direction and a second smaller cell 34 in R1 directionby the projection 19d of the driven plate 19. The viscous fluid passesthrough a gap defined between the projection 19d of the driven plate 19and the slider 29, the notches 29b of the slider 29 and the return hole27c to flow between the first smaller cell 33 and the second smallercell 34 without interruption. The viscous fluid passes through the notch29a of the slider 29 on the side of R2 to flow between the first largercell 31 and the first smaller cell 33 without interruption while itpasses through the notch 29a of the slider 29 on the side of R1 to flowbetween the second smaller cell 34 and the second larger cell 32 withoutinterruption. When the wall in the circular direction of the slider 29comes in contact with the projection 19d, however, the viscous fluid isprevented from flowing in and out in a circular direction in the slider29.

A choke C is defined between an inner circumferential surface of thestopper 27a and an outer circumferential surface 19c of the hub flange3b. When the viscous fluid passes the choke C, a large viscousresistance arises.

At a portion where the inertia element 42 is fixed to the flange 3b bythe rivet 20, a seal element 35 is sandwiched between the plate 19 andthe flange 3b, as shown in FIG. 14. The seal element 35 is made of athin annular sheet metal and has a fixing element 35a having a pluralityof holes through which the rivets 20 extend, an outer cylindricalelement 35b extending from an inner circumference of the fixing element35a toward the transmission, and an urging element 35c extending fromthe outer cylindrical element 35b to the outer circumference. The urgingelement 35c contacts an inner circumferential end of the second powerinput plate 14 close to the engine to urge the inner circumferential endof the second power input plate 14 toward the transmission under thecondition as illustrated in FIG. 14. A reaction force caused by urgingforce by the urging element 35 urges the hub flange 3 toward the engine.The seal element 35 seals the fluid space A between the second powerinput plate 14 and the hub flange 3.

A center hole at an inner circumferential end of the first power inputplate 13 engages the boss 15 and is fixed thereto by means of welding.An outer circumferential surface 15a of the boss 15 close to the engineis fitted in the center hole 2a of the flexible plate 2. Within the boss15, a center hole 15c and a hole 15b in a radial direction whichconducts to the center hole 15c and the fluid space A. A rivet 16 isinserted in the center hole 15c to seal the hole. In assembling thedevice, the center hole 15c and the hole 15b are used to fill ordischarge the viscous fluid in the fluid space A.

A bearing 17 is provided between an outer circumferential surface of theboss 15 close to the transmission and an inner circumference of a boss3a of the hub flange 3. The bearing 17 supports the boss 15 and the hubflange 3 rotatably relative to each other. A disk-like element 41 isdisposed adjacent to the bearing 17 dose to the transmission.

An inner race of the bearing 17 is fixed to a groove of the boss 15. Inthis way, the bearing 17 as well as the boss 15 is positioned in oraround a center hole 2a of the flexible plate 2. Consequently, theflexible plate 2, the boss 15 and the bearing 17 are retained in anenhanced concentric arrangement. In this embodiment, an engagement ofthe annular projection 27b of the annular housing 27 with the grooves19b of the hub flange 3b partakes of load caused between a power inputsystem and a power output system in the viscous resistance generator 25,and thus, the load imposed upon the bearing can be reduced. This leadsto downsizing the bearing 17 in a radial direction and reducing a cost.The bearing 17 is positioned within a pitch circle D (FIG. 12) of theclank bolts 6. This allows the inside of the dampening element 4 to bedesigned with less space restriction when compared to the prior art; forexample, the coil spring 22 can be put more inward, and a space requiredfor the rotation of a head of the crank bolt 16 can be easily retained.

The bearing 17 has a pair of seal elements which seal between the innerrace and an outer races. The seal element seals in lubricant between theinner race and outer race and seals the fluid space A between the boss15 and an inner circumference of the hub flange 3.

The hub flange 3 is urged toward the engine by the seal element 35, aspreviously mentioned, and this applies preload to the bearing 17. As canbe seen, the seal element 35 is a single component which has severalfunctions like sealing the fluid space A, applying the proload to thebearing 17 and the like. This leads to a decrease in the number ofcomponents and a reduction of a fabrication cost. Since the seal element35 is made of sheet metal, the cost is further reduced.

An operation of this embodiment will be described below.

When the torque is applied from the crank shaft 101 to the flexibleplate 2, the ring element 8, the power input plates 13 and 14 and thecoil spring 22 transmit it to the hub flange 3, and then the main driveshaft 102 further transmits the torque toward the transmission.Torsional vibration derived from the torque transmitted from the crankshaft 101 to the ring element 8 is partially absorbed by the flexibleplate 2 so as not to be fully transmitted to the dampening element 4.Even if the torsional vibration is transmitted, the bearing 17 and theengagement of the annular projection 27b of the annular housing 27 withthe grooves 19b of the driven plate 19 partake bending load. Thus, sincethe load applied to the bearing 17 is reduced, the bearing 17 can bedownsized in a radial direction.

Then, an operation in the event that torsional vibration has beentransmitted from the crank shaft 101 to the damper 1 will be describedbelow. The operation in the following description is directed to torquetransmitted from a power input system (the first power input plate 13,the second power input plate 14 and the annular housing 27) to a poweroutput system (hub flange 3) where relatively displaceable parts aredisplaced to absorb vibration.

When small levels of torsional vibration are experienced by the damper1' (referred to as `minute vibration` hereinafter), a small torsionalangle of displacement is observed by the relatively movable parts in thedamper. For instance, in a minute vibration a wall of the slider 29 in acircular direction does nor come into contact with the projection 19d ofthe driven plate 19, but none the less, the power input plates 13 and 14are displaced in the R2 direction from the idle state as shown in FIG.15. This displacement causes the slider 29 to move in the R2 directionwith respect to the plate 19, and the first smaller cell 33 expandswithin the slider 29 while the second smaller cell 34 contracts, asshown in FIG. 16. The viscous fluid passes the outer circumference ofthe slider 29 and the projection 19d, the notch 29b and the return hole27c to flow without interruption, and it also pass the return hole 27cto flow between the slider 29 and the fluid space A withoutinterruption.

When torsional motions continue from the state as illustrated in FIG.16, the wall of the slider 29 in a circular direction on the side of R1comes soon in contact with the projection 19d of the flange 3b, as shownin FIG. 17. After that, the slider 29 engages the driven plate 19, andthe annular housing 27 and the slider 29 are displaced relative to eachother. The second larger cell 32 and the return hole 27c are in fluidcommunication with each other in the state shown in FIG. 17, butcontinuous torsional displacement makes the projection 19d seal thereturn hole 27c, as is shown in FIG. 18.

An operation similar to that mentioned above is performed when theannular housing 27 is displaced in the R1 direction from the idle stateas shown in FIG. 15.

Under the minute vibration, the slider 29 and the annular housing 27 donot rotate relative to each other, and therefore, the viscous fluid doesnot pass the choke C. This means a large viscous resistance does notarise during the minute vibration. Under the minute vibration,additionally, the coil spring 22 expands or contracts partially pushedagainst the window hole 19a of the flange 3b and the spring receptacles13a and 14a of the power input plates 13 and 14; and thus, a lowrigidity is attained. Specifically, under the minute vibration,characteristics of the low rigidity and low viscous resistance can beattained, and they are effective to suppress abnormal sound likeclattering sound, heavy sound or the like.

An operation in transmitting torsional vibration of a large torsionalangle (referred to as `grand vibration` hereinafter) will now bedescribed.

It is now assumed that the annular housing 27 from the idle state asshown in FIG. 12 is displaced relative to the driven plate 19 in the R2direction. Accordingly, the slider 29 is shifted toward R2, and thedisplacements proceed as described above with respect to the minutevibration as illustrated in FIGS. 15 to 18. When the second larger cell32 on the side of R2 is sealed between the slider 29 and the projection19d of the flange 3b as shown in FIG. 18, the second larger cell 32begins to contract. This results in the viscous fluid in the secondlarger cell 32 passing the choke C to flow into the arcuate fluidsub-chamber B1 in the R1 direction (FIG. 19). When the viscous fluidflows through the choke C, a large viscous resistance is experienced.The viscous fluid passes the return hole 27c and smoothly flows into thefirst larger cell 31. Thus, the annular fluid chamber B is always filledwith sufficient amount of the viscous fluid.

When displaced from the state as illustrate in FIG. 19 in the R1direction, the annular housing 27 passes by an intermediate position toperform reverse displacement operation to that in FIG. 19.

As has been described, a large viscous resistance is obtained under thegrand vibration. In addition to that, the rigidity is enhanced becausethe seat element 23 of the coil spring 22 contacts an end of the windowhole 19a and ends of the spring receptacles 13a and 14a of the powerinput plates 13 and 14 as the torsional angle becomes larger. Thus,under the grand vibration, characteristics of a high rigidity and alarge viscous resistance are obtained, and this effectively dampensvibration upon tip-in-tip-out (large vibration forward and backward ofan automobile caused by rapid operation of an accelerating pedal).

It is assumed now that the minute vibration is transmitted under thecondition that the annular housing 27 is distorted toward R2 by aspecified angle relative to the hub flange 3. The slider 29 repeatsreciprocal torsional motions to the projection 19d in an angular rangewhere the wall in a circular direction of the slider 29 does not come incontact with the projection 19d. In such a situation, the viscous fluiddoes not flow at the choke C nor cause a large viscous resistance. Thus,even with such a condition that the annular housing 27 and the hubflange 3 make a large torsional angle, the minute vibration can beeffectively absorbed.

In this embodiment, the flange 3b of the hub flange 3 extends toward theouter circumference engaging the dampening element 4. Thus, the largedriven plate typically used in the prior art can be omitted to simplifythe configuration, and this leads to a cost reduction. Moreover, sincean outer circumferential end of the flange 3b engages the viscousresistance generator 25, the above-mentioned effect is reinforced.Furthermore, since the outer circumference of the flange 3b is insertedin the annular fluid chamber B, the above-mentioned effect isincreasingly reinforced.

Third Embodiment

FIG. 20 shows a damper 101 in accordance with a third embodiment of thepresent invention. The damper 101 is a device which transmits torquefrom a crankshaft 301 in an engine to a main drive shaft 302 in atransmission to dampen torsional vibration. In FIG. 20, the engine (notshown) is positioned on the left of the drawing while the transmission(not shown) is positioned on the right. Line O--O in FIG. 20 is an axialline of rotation by the damper 101.

The damper 101 primarily includes a flexible plate 102, a ring element108 fixed to the flexible plate 102, a hub flange 103, and a dampeningelement 104 elastically coupling the ring element 108 and the hub flange103 in a circular direction to dampen torsional vibration between them.

The flexible plate 102 is a roughly disk-like element which is flexiblein axial directions and is generally rigid in a radial direction. Theflexible plate 102 has a center hole 102a at its center. The flexibleplate 102 has a plurality of window holes 102b formed at spaced apartintervals in the circular direction in an intermediate portion in aradial direction. A plurality of bolt holes 102c are formed at the sameintervals in the circular direction inward from the window holes 102b. Abolt 6 extending through each of the bolt holes 102c fix an innercircumferential end of the flexible plate 102 to a tip of the crankshaft301. Moreover, an outer circumference of the flexible plate 102 close tothe engine, a plurality of arcuate inertial elements 7 are fixed byrivets 51. The inertia elements 7 are useful to increase moment ofinertia of the damper 101. The inertia elements 7 are respectivelyshaped by dividing an annular element into sections in the circulardirection, and thus, flexibility of the flexible plate 102 in a bendingdirection is assuredly retained.

An outer circumferential end of the flexible plate 102 is fixed to thering element 108 by a plurality of bolts 10 with a disk-shaped plate 109interposed between them. The inertia elements 7 respectively havenotches corresponding to the bolts 10. The hub flange 103 is made upwith a boss 103a and a flange 103b integrally formed along an outercircumference of the boss 103a. The boss 103a extends toward the engineand is provided at its center with a spline hole 103c which meshes withspline teeth formed in the main drive shaft 302 extending from thetransmission. A cap-shaped element 41 is fixed at a center hole of theboss 103a close to the engine to stop up the hole.

The dampening element 104 primarily includes a first power input plate113, a second power input plate 114, a driven plate 119, a coil spring22 and a viscous resistance generator 125.

The first power input plate 113 and the second power input plate 114 aredisk-like sheet metal elements. The first power input plate 113 iscomprised of a disk element 113a and a hollow cap 113b protruding from acenter of the disk element 113a toward the engine. The hollow cap 113bis drawn from the center of the disk element 113a to shape in a unitaryfashion. The second power input plate 114 has its outer circumferenceextending toward the engine, and it has a cylindrical wall fixed to anouter circumferential end of the first power input plate 113. Thecylindrical wall is welded to an inner circumference of the ring element108. The first power input plate 113 and the second power input plate114 define a fluid space A (not shown in FIG. 20, but the space A issimilar to that in previously described embodiments) accommodating adriven plate 119, a coil spring 22, a viscous resistance generator 125and so forth. The fluid space A is filled with viscous fluid.

The driven plate 119 is a disk-like element, having its innercircumferential end coupled to the flange 103b of the hub flange 103 bya plurality of rivets 20. A plurality of window holes 119a extending ina circular direction are formed in an intermediate portion of the drivenplate 119 in a radial direction. Moreover, annular grooves 119b areformed on opposite surfaces of an outer circumferential end of thedriven plate 119. A plurality of projections 119b expand outward in aradial direction from an outer circumferential surface 119c of thedriven plate 119.

The coil spring 122 is a combination of small and large coil springs andis put in the window hole 119a of the driven plate 119. Seat elements(not shown) are placed at opposite ends of the coil spring 122. Thefirst and second power input plates 113 and 114 are respectivelyprovided with spring receptacles 113d and 114d corresponding in positionto the window hole 119a of the driven plate 119. The seat elements comein contact with opposite ends of the spring receptacles 113d and 114d ina circular direction, respectively. In this way, the first and secondpower input plates 113 and 114 are elastically coupled to each other inthe circular direction with the coil spring 122 intervening betweenthem. The coil spring 122 is housed in the window hole 119a and thespring receptacles 113a and 114a, being partially pushed against them.

The viscous resistance generator 125 will be described below. Theviscous resistance generator 125 has an annular housing 127 positionedin an outermost circumference within the fluid space A, a plurality ofpins 28 connecting the annular housing 127 to the first and second powerinput plates 113 and 114, and a plurality of slider (not shown, butsimilar to that described in previous embodiments) arranged within thehousing 127. The sliders divide the annular fluid chamber B (not shown,but similar to that described in previous embodiments) into a pluralityof arched fluid sub-chambers. The stoppers respectively have the holesthrough which the pins 28 extend.

The annular housing 127 is positioned inside an outer circumferentialwall of the second power input plate 114 and is interposed at itsopposite end surfaces in an axial direction between the power inputplates 113 and 114. An opening extending in the circular direction isformed at an inner circumference of the annular housing 127, and anouter circumference of the driven plate 119 extends into the opening.Each of the pins 28 has its opposite ends engages with the first andsecond power input plains 113 and 114, respectively, so as not to rotateby itself. This permits the annular housing 127 and the power inputplates 113 and 114 rotate as a unity. A width of the annular housing 127which determines a viscous resistance depends upon a length of a shankof the pin 128.

In an inner end of the annular housing 127 in a radial direction,opposing annular projections 127b (surrounding the opening mentionedabove) which protrudes inward at an inner end of the annular housing 127in the radial direction, and the projections 127b are fitted in annulargrooves 119b formed in the driven plate 119 to seal an inner opening ofthe annular fluid chamber B. The projection 127b is an engagementportion fitted in the annular grooves 119b formed in the driven plate119 and partakes of load (thrust load, radial load and bending load)caused between a power input system (the first and second power inputplates 113 and 114 and the housing 127) and a power output system (thedriven plate 119 and the hub flange 103) together with a bearing 117,described below, with the viscous fluid intervening therebetween.

The present embodiment also includes a number of features that may notbe shown in FIG. 20, but are shown and described in the previousembodiments, such as return holes 27c, projections 119d (whichcorrespond to projections 19d in previous embodiments), a cap-like slide29. Configuration of the slider 29 and a viscous fluid element 125 aregenerally the same as those of the slider 29 and the viscous resistancegenerator 125 in the above Embodiment 1.

An inner circumference of the driven plate 119 and the flange 103b ofthe hub flange 103 are fixed to each other by the rivets 20 with aspring seal 35 sandwiched between them. The spring seal 35 is generallythe same as the spring seal described with respect to FIGS. 4 and 14above.

The boss 113b of the first power input plate 113 is inserted in the hole102a of the flexible plate 102. Thus, the first power input plate 113 ispositioned by the flexible plate 102.

The bearing 117 is placed between an inner circumference of the diskelement 113a of the first power input plate 113 and an outercircumference of the boss 103a of the hub flange 103. The bearing 117has its outer race fixed to the first power input plate 113 by anannulus fixing element 152 and a rivet 153. The boss 103a is insertedinside an inner race of the bearing 117 and partially comes in contactwith an end surface of the inner race close to the transmission. In thisway, the first power input plate 113 is positioned in the center hole102a of the flexible plate 102 and supports the bearing 117. This allowsthe flexible plate 102, the first power input plate 113, the bearing 117and the hub flange 103 to lie in a generally concentric arrangement.

In this embodiment, the bearing 117 is placed within a pitch circle ofbolts 6 fixing the flexible plate 102 to the crankshaft 301, and theinside of the dampening element 104 can be designed with lessrestriction. For example, the driven plate 119 may expand toward theinner circumference or the coil spring 22 may be placed more inward. Aspace for rotations of a head of the bolt 6 can be retained.

The bearing 117 has a seal element between the inner race and the outerrace at its opposite end surfaces. This seal element seals in lubricantbetween the inner race and the outer race and seals the fluid space Abetween the inner circumference of the first power input plate 113 andthe boss 103a of the hub flange 103.

The hub flange 103 is urged toward the engine by the spring seal element135, as previously mentioned, The hub flange 103 applies force towardthe engine to the bearing 117 to impose preload upon it. As can be seen,the seal element 35 is a single component which has several functionslike sealing the fluid space A, applying the preload to the bearing 17and the like. This leads to a decrease in the number of components and areduction of a fabrication cost. Since the seal element 35 is made ofsheet metal, the cost is further reduced.

Also, in this embodiment, the boss 103a of the hub flange 103 isinserted in the hollow cap 113b of the first power input plate 113. Thisallows the damper 101 to reduce the total dimension in an axialdirection. Additionally, since the bearing 117 is positioned between theinner circumference of the first power input plate 113 and the outercircumference of the boss 103a, the bearing 117 can be further downsizedin a radial direction, This also brings about a cost reduction.

A first inertia element 142 is provided on the flange 103b of the hubflange 103 close to the transmission. The first inertial element 142 isa disk-like element covering the second power input plate 114 close tothe transmission and has its inner circumferential end fixed to theflange 103b and the driven plate 119. A second inertia element 144 isfixed to the first inertia element 142 close to the transmission by arivet 143. The second inertial element 144 is a disk-like element whichcomes in contact with the first inertial element 142 close to thetransmission. The first and second inertial elements 142 and 144 areuseful to increase moment of inertia of the power output system. A ringgear 111 to start the engine is welded to an outer circumference of thefirst inertia element 142. The ring gear 111 is shifted from the powerinput system to the power output system as in this embodiment toincrease a inertial moment ratio of the power output system can beeasily increased. When the inertial moment ratio of the power outputsystem is increased, it is possible to decrease a resonance frequencydown to an idling speed (a practical number of revolutions) or below ina drive system including the damper 101. With the ring gear 111positioned as in the current embodiment, a cost reduction is attained ascompared to the prior art.

The operation of the damper is almost the same as that in the aboveEmbodiment 2, and therefore description of the operation is omitted.

Fourth Embodiment

FIG. 21 shows a damper 1 in a fourth embodiment of the presentinvention. The damper 1 is a device which transmits torque from acrankshaft 301 in an engine to a main drive shaft 302 in a transmissionto dampen torsional vibration. In FIG. 21, the engine (not shown) isplaced on the left of the drawing while the transmission (not shown) isplaced on the right. Line O--O in FIG. 21 is an axial line of rotationby the damper 1. R1 in FIG. 2 denotes the direction of the rotation bythe damper 1 (clockwise).

The damper 1 primarily includes a flexible plate 2, a ring element 8fixed to the flexible plate 2, a hub flange 3, and a dampening element 4elastically coupling the ring element 8 and the hub flange 3 in acircular direction to dampen torsional vibration between them.

The flexible plate 2 is a roughly disk-like element which is flexible inaxial directions and is generally rigid in a circular direction. Theflexible plate 2 has a center hole 2a at its center. The flexible plate2 has a plurality of window holes 2b formed at the same intervals in thecircular direction in intermediate portions in a radial direction. Aplurality of bolt holes 2c are formed at the same intervals in thecircular direction inward from the window holes 2b. A bolt 6 extendingthrough each of the bolt holes 2c fixes an inner circumferential end ofthe flexible plate 2 to a tip of the crankshaft 301. Moreover, in anouter circumference of the flexible plate 102 close to the engine, aplurality of arched inertial elements 7 are fixed by rivets 51. Theinertia elements 7 are useful to increase moment of inertia of thedamper 1. The inertia elements 7 are respectively shaped by dividing anannular element into sections in the circular direction, and thus,flexibility of the flexible plate 2 in a flexural direction is assuredlyretained.

An outer circumferential end of the flexible plate 102 is fixed to thering element 8 by a plurality of bolts 10 with a disk-shaped plate 9interposed between them. The inertia elements 7 respectively havenotches corresponding to the bolts 10.

The hub flange 3 is made up with a boss 3a and a flange 3b integrallyformed along an outer circumference of the boss 3a. The boss 3a extendsfrom the flange 3b toward the engine and is provided at its center witha spline hole 3c which meshes with spline teeth of the main drive shaft302 extending from the transmission. The flange 3b has its intermediateportion in a radial direction cylindrically protruding toward theengine, and it still expands from a distal end of a cylindrical portiontoward the outer circumference.

The dampening element 4 primarily includes a first power input plate 13,a second power input plate 14, a driven plate 19, a coil spring 22 and aviscous resistance generator 25.

The first power input plate 13 is comprised of a disk element 13a and acenter cap 13b welded to the center of the disk element 13a. In an innercircumference of the disk element 13a, there lie a plurality of holes13c. A cap 52 is fitted in each of the holes 13c which are arrangedclose to an outer race of a bearing 17 mentioned later. The cap 52 ispull out from the hole 13c to fill or discharge a fluid space A withviscous fluid, as is mentioned below. An inner circumferential end ofthe disk element 13a is bent toward the transmission and welded to acenter cap 13b. In such a condition, the center cap 13b has acylindrical portion 13e expanding further from the disk element 13atoward the transmission. The center cap 13b close to the engine isfitted in the center hole 2a of the flexible plate 2.

The second power input plate 14 has in its outer circumference acylindrical wall fixed to the outer circumferential end of the firstpower input plate 13. The cylindrical wall is welded to an innercircumference of the ring element 8. The first power input plate 13 andthe second power input plate 14 define the fluid space A accommodating adriven plate 19, a coil spring 22, a viscous resistance generator 25 andso forth. The fluid space A is filled with the viscous fluid.

The driven plate 19 is a disk-like element, having its innercircumferential end coupled to the flange 3b of the hub flange 3 by aplurality of rivets 20. A plurality of window holes 19a extending in thecircular direction are formed in intermediate portions of the drivenplate 19 in a radial direction. Moreover, annular grooves 19b are formedon opposite surfaces of an outer circumferential end of the driven plate19. A plurality of projections 19d expand outward in a radial directionfrom an outer circumferential surface 19c of the driven plate 19.

The coil spring 22 is a combination of small and large coil springs andis put in each of the window holes 19a of the driven plate 19. Seatelements 23 are placed at opposite ends of the coil spring 22. The firstand second power input plates 13 and 14 are respectively provided withspring receptacles 13d and 14d corresponding in position to the windowholes 19a of the driven plate 19. The seat elements 23 come in contactwith opposite ends of the spring receptacles 13d and 14d in the circulardirection, respectively. In this way, the first and second power inputplates 13 and 14 are elastically coupled to each other in the circulardirection with the coil spring 22 intervening between them. In an idlestate, the seat elements 23 have their respective inner circumferencesalone come in contact with ends of the spring receptacles 13d and 14d ofthe power input plates 13 and 14 and an end of the window hole 19a ofthe driven plate 19. Thus, the coil spring 22 is housed in the windowhole 19a and the spring receptacles 13a and 14a, being partially pushedagainst them.

The viscous resistance generator 25 will now be described although manyof the components are similar or the same as components in the previousembodiments described above.

The viscous resistance generator 25 is comprised of an annular housing27 provided at an outermost circumference within the space A, aplurality of pins 28 coupling the housing 27 to the first and secondpower input plates 13 and 14, and a plurality of sliders 29 providedwithin the housing 27.

The annular housing 27 is placed inside a cylindrical outercircumferential wall of the second power input plate 14 and has itsopposite end surfaces in an axial direction interposed between the powerinput plates 13 and 14. There lies an opening close to an innercircumference of the annular housing 27, extending in the circulardirection, and an outer circumference of the driven plate 19 is insertedin the opening. Within the annular housing 27, there is provided anannular fluid chamber B which is filled with the viscous fluid. Withinthe annular housing 27, additionally, a plurality of stoppers 27a areintegrally formed at the same intervals in the circular direction, andthey divide the annular fluid chamber B in a plurality of arched fluidsub-chambers B1. The stoppers 27a respectively have holes through whichthe pins 28 are inserted. The pins 28 have their respective oppositeends meshed with the power input plates 13 and 14 so as not to rotate bythemselves. This allows the annular housing 27 to revolve integral withthe first and second power input plates 13 and 14. A width of theannular housing 27 which determines a viscous resistance depends upon alength of a shank of the pins 28.

The annular housing 27 is provided at its inner end in a radialdirection with opposing annular projections 27b (surrounding the openingmentioned above) which protrude inward at an inner end of the annularhousing 27, and the projections 27b are fitted in the annular grooves19b formed in the driven plate 19 to seal an inner circumference of theannular fluid chamber B. The projections 27b are engagement portionsfitted in the annular grooves 19b and partake of load (thrust load,radial load and bending load) caused between a power input system (thefirst and second power input plates 13 and 14 and the annular housing27) and a power output system (the driven plate 19 and the hub flange 3)with the viscous fluid intervening therebetween.

Return holes 27c are formed in inner opposite end surfaces ofintermediate portions in a radial direction between the stoppers 27a,and the return holes 27c permit the viscous fluid to move between theannular fluid chamber B and the inner space A without interruption. Inan idle state, the projections 19d of the driven plate 19 are arrangedcorresponding in position to the return holes 27c.

Within the arched fluid chambers B1, cap-like sliders 29 of resin areattached to cover the projections 19d of the driven plate 19 from theouter circumference. Each of the slider 29 has an outer circumferencefitted in an inner circumference of the annular housing 27, and it isplaced movable in a circular direction in each of the arched fluidchamber B1 (not shown in FIG. 21). The slider 29 is movable in thecircular direction in a range where a wall in the circular direction isnot in contact with the projection 19d of the driven plate 19. Theslider 29 has notches 29a radially inside opposite walls in the circulardirection. There also lie notches 29b radially inside opposite walls ofthe slider 29 in an axial direction. An interior portion of the slider29 in a radial direction comes in contact with the annular projection27b of the annular housing 27.

Each of the arcuate fluid sub-chambers B1 is further divided into afirst larger cell similar to the cell 31 in the first embodiment, asecond larger cell 32 by the slider 29, similar to the first embodimentdescribed above. The slider 29 is divided into a first smaller cell 33and a second smaller cell 34 by the projection 19d of the driven plate19, again similar to the first embodiment described above. Theembodiment depicted in FIG. 21 also includes the following elements andfeatures which may not be shown, but are similar or the same ascorresponding elements in the first embodiment described above: a gapdefined between the projection 19d of the driven plate 19 and the slider29, the notch 29b of the slider 29 and the return hole 27c permit theviscous fluid to move from the first smaller cell 33 to the secondsmaller cell 34 and vice versa; the viscous fluid passes the notch 29aof the slider 29 on the R2 side to flow between the first larger cell 31and the first smaller cell 33 while it passes the notch 29a of theslider 29 on the R1 side to flow between the second smaller cell 34 andthe second larger cell 32; when the wall of the slider 29 in thecircular direction comes in contact with the projection 19d, however,the viscous fluid is blocked so as not to flow from or into the slider29 in the circular direction; a choke C is provided between an innercircumferential surface of the stopper 27a and an outer circumferentialsurface 19c of the driven plate 19; when the viscous fluid passes thechoke C, a large viscous resistance arises; an inner circumference ofthe driven plate 19 and the flange 3b of the hub flange 3 are fixed toeach other by the rivets 20 with a spring seal 35 intervening betweenthem; the spring seal 35 is an annulus ring of thin sheet metal andincludes a fixing portion 35a having a plurality of holes through whichthe rivets 20 are fitted, an outer cylindrical portion 35b extendingfrom an outer circumference of the fixing portion 35a toward thetransmission, and a resilient portion 35c spreading outward from theouter cylindrical portion 35b. The resilient portion 35c is in contactwith an inner circumferential end of the second power input plate 14 ona side close to the engine to urge the inner circumferential end of thesecond power input plate 14 toward the transmission, A reaction forcecaused by such urging force urges the driven plate 19 and the hub flange3 toward the engine. The spring seal 35 seals the fluid space A betweenthe inner circumference of the second power input plate 14 and theflange 3b of the hub flange 3.

The bearing 17 is placed between an outer circumferential surface of acylindrical portion 13e of the center cap 13b and an inner circumferenceof a cylindrical portion of the flange 3b. The bearing 17 supports thehub flange 3 rotatably relative to the center cap 13b. An inner race ofthe bering 17 is fitted in an outer circumference of the cylindricalportion 13e to come in contact with an inner circumferential end surfaceof the disk element 13a. An outer race of the bearing 17 is pressed intoan inner circumferential surface of the flange 3b. Thus, the bearing 17as well as the center cap 13b is positioned at the center hole 2a of theflexible plate 2. Consequently, the flexible plate 2, the center cap 13band the bearing 17 are arranged to each other increasingly concentric.

Since engagement of the annular projection 27b of the housing 27 and thegrooves 19b of the driven plate 19 in the viscous resistance generator25 partakes of load caused between the power input system and the poweroutput system, the load imposed on the bearing 17 can be reduced. Thus,dimensions of the bearing 17 can be reduced in a radial direction, and acost can be decreased.

The bearing 17 has seal element at its opposite ends to seal between theinner race and an outer race. The seal element tightly seals inlubricant between the inner race and the outer race and seals the fluidspace A between the center cap 13b and the hub flange 3.

A bearing 53 is placed inside the center cap 13b dose to the engine. Thebearing 53 rotatably supports a tip of the main drive shaft 302. Thus,the bering 53 facilitates supporting the main drive shaft 302.

The hub flange 3 is urged by the spring seal 35 toward the engine, asmentioned above, and thus, the hub flange 3 impose preload toward theengine upon the bearing 17. As can be seen, the seal element 35 is asingle component which has several functions like sealing the fluidspace A, applying the preload to the bearing 17 and the like. This leadsto decrease in the number of components, simplification of aconfiguration and a reduction of a fabrication cost. Since the sealelement 35 is made of sheet metal, the cost is further reduced.

A first inertia element 42 is provided in the flange 3b of the hubflange 3 close to the transmission. The first inertial element 42 is adisk-like element covering the second power input plate 14 close to thetransmission and has its inner circumferential end fixed to the flange3b and the driven plate 19 by the rivets 20. A ring gear 11 is welded toan outer circumference of the first inertia element 42. Although thering gear 11 is an element welded to the outer circumference of the ringelement 8 in the prior art embodiment, shifting it from the power inputsystem to the power output system as in this embodiment, moment ofinertia of the power output system can be easily increased. When themoment of inertia of the power output system is increased, it ispossible to decrease a resonance frequency down to an idling speed (apractical number of revolutions) or below in a drive system includingthe damper 1. With the ring gear 11 as has been used in the prior art, acost reduction is attained.

A disk-shaped second inertia element 44 is fixed to the first inertialelement 42 close to the transmission by a plurality of rivets 43.

Advantages in fabricating and assembling the power transfer device willnow be described.

The disk element 13a and the center cap 13b are fixed to each other bymeans of welding, and the center cap 13b has the cylindrical portion 13eprotruding toward the transmission. In such a configuration, fabricationof the cylindrical portion 13e for supporting the inner race of thebearing 17 is facilitated, and this leads to reduction of a fabricationcost.

Further in this embodiment, the holes 13c are formed corresponding inposition to the outer race of the bearing 17 in an inner circumferenceof the disk element 13a. The holes 13c are utilized to press the outerrace of the bearing 17 into the inner circumference of the flange 3b ofthe hub flange 3. Specifically, the bearing 17 before pressed in has itsinner race fitted in the cylindrical portion 13e of the center cap 13b.The outer race under such a condition is pressed in the innercircumference of the flange 3b by pushing a driver into the hole 13c. Inthis manner, attachment of the bearing 17 is facilitated.

Fifth Embodiment

FIG. 22 shows a damper 101 in accordance with a fifth embodiment of thepresent invention. The damper 101 is a device which transmits torquefrom a crankshaft 301 in an engine to a main drive shaft 302 in atransmission and dampens torsional vibration between them. Referring toFIG. 22, the engine (not shown) is placed on the left of the drawingwhile the transmission (not shown) is on the right. Line O--O of FIG. 22is an axial line of rotation by the damper 101.

The damper 101 primarily includes a flexible plate 102, a ring element108 fixed to the flexible plate 102, a hub flange 103, and a dampeningelement 104 elastically coupling the ring element 108 and the hub flange103 in a circular direction to dampen the torsional vibration betweenthem.

The flexible plate 102 is a roughly disk-shaped element which isflexible in axial directions and is generally rigid in a rotationaldirection. An inner circumferential end of the flexible plate 102 isfixed to a tip of the crankshaft 301 by a bolt 106. An outercircumferential end of the flexible plate 102 is fixed to the ringelement 108 by a plurality of bolts 110.

The hub flange 103 is comprised of a boss 103a and a flange 103bintegrally formed along an outer circumference of the boss 103a. At thecenter of the boss 103a, a spline hole 103c in which spline teeth of themain drive shaft 302 expanding from the transmission is formed.

The dampening element 104 primarily includes a first power input plate113, a second power input plate 114, a driven plate 119, a coil spring122 and a viscous resistance generator 125.

The first and second power input plate 113 and 114 are disk-likeelements of sheet metal The first power input plate 113 has a diskelement 113a and a boss 113b protruding from the center of the diskelement 113a toward the engine. The boss 113b is drawn from the diskelement 113a and shaped unitarily. The second power input plate 114 hasat its outer circumferential end an outer circumferential wall whichexpands toward the engine and is fixed to an outer circumferential endof the first power input plate 113. The outer circumferential wall isfixed to an inner circumference of the ring element 108. The first andsecond power input plates 113 and 114 and the hub flange 103 defined afluid space A filled with fluid. A hole 113c is formed at the center ofthe boss 113b, and a cap 143 is fitted in the hole 113c. The hole 113cis used to fill or discharge the fluid space A with viscous fluid. Acap-like seal element 141 is fixed at a center hole of the boss 103close to the engine. The seal element 141 seals the fluid space A at thecenter of the boss 103a.

The driven plate 119 consists of two disk-shaped elements 119A and 119Band has its inner circumferential end coupled to the flange 103b of thehub flange 3 by a plurality of rivets 120. At center portions in radialdirections in the driven plate 119, a plurality of window holes 119a areformed, extending in a circular direction. In opposite sides of an outercircumferential end of the driven plate 119, annular grooves 119b areformed, respectively. A plurality of projections 119d expand outward inthe radial directions from a outer circumferential surface 119c of thedriven plate 119.

The coil spring 122 is of a combination of large and small coil springsand is positioned in each of the window holes 119a of the driven plate119. Seal elements 123 are provided at opposite ends of the coil spring122. Spring receptacles 113d and 114d are formed corresponding inposition to each of the window holes 119a of the driven plate 119 in thefirst and second power input plates 113 and 114, respectively. The seatelements 123 contact with opposite ends of the spring receptacles 113dand 114d in the circular direction, In this way, the first and secondpower input plates 113 and 114 and the driven plate 119 are elasticallycoupled to each other in the circular direction with the coil springs122 intervening between them. Under an idle state, each of the seatelements 123 is in contact only at its inner circumference with ends ofthe spring receptacles 113d and 114d of the power input plates 113 and114 and an end of the window hole 119a of the driven plate 119 (similarto the first embodiment depicted in FIG. 2). Specifically, the coilspring 122 is housed in the window hole 119a and the spring receptacles113d and 114d, being partially pushed against them.

The viscous resistance generator 125 will now be described. The viscousresistance generator 125 includes an annular housing 127 positioned inan outermost circumference in the fluid space A, a plurality of pins 128coupling the annular housing 127 to the first and second power inputplates 113 and 114, and a plurality of slides 129 put in the annularhousing 127.

The annular housing 127 is placed inside an outer circumferential wallof the second power input plate 114 and has its opposite end surfaces inan axial direction interposed between the first and second power inputplates 113 an 114. An opening extending in the circular direction isformed in an inner circumference of the annular housing 127, and anouter circumference of the driven plate 119 is inserted in the opening.Within the annular housing 127, an annular fluid chamber filled withviscous fluid is formed. Also within the annular housing 127, aplurality of stoppers 127a are disposed at the same intervals in thecircular direction. The stoppers 127 divide the annular fluid chamberinto a plurality of arched fluid sub-chambers. Each of the stoppers 127ahas a hole through which a pin 128 extends. The pin 128 has its one endengaged with the second power input plate 114 so as not to rotate, and atip of a bolt 110 is inserted in the pin 128. This permits the annularhousing 127 to rotate along with the first and second power input plates113 and 114 and the ring element 108 in a unity.

There is provided an annular projection 127b which protrudes inward atan inner end of the annular housing 27 in a radial direction(surrounding the opening mentioned above), and the projection 127b isfitted in the annular grooves 119b formed in the driven plate 119 toseal the inner circumference of annular fluid chamber. Engagement of theannular projection 127b with the grooves 119b takes load (thrust load,radial load and bending lead) caused between a power input system (thefirst and second power input plates 113 and 114 and the annular housing127) and a power output system (the driven plate 119 and the hub flange103), with the viscous fluid intervening among them. Especially, sincethe annular projection 127b and the grooves 119b expand in the circulardirection for engagement, the engagement partakes of the radial loadbetween the power input system and the power output system as a bearingdoes in the prior art. Consequently, the bearing is omitted in thisembodiment. This brings about simplification of the configuration of thepower transfer device and decrease in a cost.

The sliders 129 are cap-shaped elements covering the projections 119d ofthe driven plate 119 from an outer circumferential side. Structural andfunctional characteristics of the sliders 129 are the same as those ofthe sliders illustrated in the above firs embodiment, and thedescription about them is omitted herein.

An inner circumference of the driven plate 119 and the flange 103b ofthe hub flange 103 are fixed to each other by the rivets 120 with aspring seal 135 sandwiched between them. The spring seal 135 is anannulus ring of thin sheet metal and is comprised of a fixing portionfixed by the rivets 120 and a seal portion which expands from the fixingportion to the outer circumference till coming in contact with an innercircumferential end of the second power input plate 114 to seal betweenthe flange 103b and the inner circumferential end of the second powerinput plate 114.

An inertia element 142 is provided in the flange 103b of the hub flange103 close to the transmission. The inertia element 142 is a disk-likeelement covering the second power input plate 114 close to thetransmission and has its inner circumferential end fixed to the flange103b and the driven plate 119 by the rivets 120. With the inertiaelement 142, moment of inertia of the power output system is increased.A ring gear 11 is welded to an outer circumference of the inertiaelement 142. Although the ring gear 111 is an element welded to an outercircumference of the ring element 108 in the prior art, shifting it fromthe power input system to the power output system as in this embodimentfacilitate increasing the moment of inertia of the power output system.When a inertia moment ratio of the power output system is increased, itis possible to decrease a resonance frequency down to an idling speed (apractical number of revolutions) or below in a drive system includingthe damper 101. With the ring gear 11 as in the current embodiment, acost reduction is attained when compared to the prior art.

An operation of this device is the same as that in the previousembodiment, and description about it is omitted.

Sixth Embodiment

FIGS. 23, 24 and 25 show a damper 1" in accordance with a sixthembodiment of the present invention. The damper 1" is a device whichtransmits torque from a crankshaft 301 in an engine to a main driveshaft 302 in a transmission. Referring to FIG. 23, the engine (notshown) is positioned on the left of the drawing while the transmission(not shown) is positioned on the right. Line O--O in FIG. 23 is an axialline of rotations by the damper 1", and R1 denotes a direction of therotations by the damper 1" (clockwise).

The damper 1 primarily includes a flexible plate 2, a hub flange 3, anda dampening element 4 which elastically couples the flexible plate 2 andthe hub flange 3 in a circular direction and dampens torsional vibrationbetween them.

The flexible plate 2 is a roughly disk-shaped element which is flexiblein a flexural direction and is generally rigid in a rotationaldirection. The flexible plate 2 has a center hole 2a at its center. Theflexible plate 2 is provided at its inner circumference with a pluralityof bolt holes 2b at the same intervals in a circular direction. Bolts 6extending through the bolts holes 2b fix an inner circumferential end ofthe plate 2 to a tip of the crankshaft 301. An outer circumferential endof the flexible plate 2 is fixed to a ring element 9 by a plurality ofbolts 10. Outer circumferential ends of a first power input plate 13 anda second power input plate 14, described below, are interposed betweenan outer circumference of the flexible plate 2 and the ring element 9;that is, the first and second power input plates 13 and 14 are fixed tothe flexible plate 2.

The hub flange 3 includes a boss 3a and a flange 3b integrally formedalong an outer circumference of the boss 3a. The boss 3a is provided atits center with a spline hole 3c which engages spline teeth of the maindrive shaft 302 extending from the transmission. A cap element 41 isfixed in a center hole of the boss 3c close to the engine.

An inner circumferential end of a disk-like inertia element 40 is fixedto the hub flange 3b by a plurality of rivets 21. The disk-like inertiaelement 40 has an annular projection 40a which protrudes, keeping offthe center in a radial direction slightly closer to the innercircumference, toward the engine. The inertia element 42 is fixed to anouter circumference of the disk-like inertial element 40 close to theengine by a plurality of rivets 43. The disk-like inertia element 40 hasan outer circumferential cylinder 40c extending toward the engine. Aring gear 11 to start the engine is fixed to an outer circumference ofan outer circumferential cylinder 40c.

The dampening element 4 primarily includes the first power input plate13, the second power input plate 14, a driven plate 19, a coil spring 22and a viscous resistance generator 25.

The first and second power input plates 13 and 14 are disk-shapedelements of sheet metal and have their respective outer circumferencesfixed to the flexible plate 2 and the ring element 9, as mentionedbefore. The first and second power input plates 13 and 14 define a fluidspace A accommodating the driven plate 19, the coil springs 22, theviscous resistance generator 25 and so forth. The fluid space A isfilled with viscous fluid.

The first power input plate 13 includes a disk element 13a and a centercap 13b protruding from the center of the disk element 13 toward theengine. The center cap 13b is drawn from the disk element 13a to shapein a unity. A hole 13c is formed at a center of tip of the center cap13b. A plurality of inertia elements 8 are fixed to an outercircumference of the disk element 13a of the first power input plate 13close to the engine.

A bearing 17 is positioned between the inner circumference of the firstpower input plate 13 and an inner circumference of the disk-like inertiaelement 40. The bearing 17 supports the disk-like inertia element 40 atits inner circumference rotatably relative to the first power inputplate 13.

An annular fixing element 52 which is L-shaped in cross section is fixedin the inner circumference of the disk element 13a of the first powerinput plate 13. The annular fixing element 52 supports an inner race ofthe bearing 17. An outer race of the bearing 17 is held inside theannular projection 40a of the disk-like inertia element 40. The bearing17 has a seal element of which opposite end surfaces are used to sealbetween the inner race and the outer race. The seal element seals inlubricant between the inner race and the outer race and seals the fluidspace A between the inner circumference of the first power input plate13 and the inner circumference of the disk-like inertia element 40.

The second power input plate 14 has a large center hole. An innercircumferential end 14a of the second power input plate 14 is benttoward the engine. The inner circumferential end 14a is close to theouter circumference of the annular projection 40a of the disk-likeinertia element 40. The inner circumferential end 14a of the secondpower input plate 14 can be slightly deformed, so that pressure withinthe fluid space A causes it to continuously contact with the annularprojection 40a.

The driven plate 19 is a single disk-shaped element of sheet metal andhas its inner circumferential end fixed to the annular projection 40a ofthe disk-like inertia element 40 by a plurality of rivet 20. Inintermediate portions of the driven plate 19 in radial directions, asshown in FIG. 24, a plurality of window hole 19a extending in a circulardirection. Surrounding the entire circumferential extension of each ofthe window holes 19a, a flap 19b is formed raised extending toward thetransmission. A plurality of projections 19c protrude outward in radialdirections from an outer circumferential surface of the driven plate 19.At a tip of each of the projections 19c, a flap 19d is formed, beingbent toward the transmission.

A coil spring 22 is a combination of large and small coil springs, andit is positioned in each of the window holes 19a of the driven plate 19.At opposite ends of the coil spring 22, seat elements 23 are attached.The first and second power input plates 13 and 14 are respectivelyprovided with spring receptacles 13d and 14d corresponding in positionto the window holes 19a of the driven plate 19. The seat elements 23come in contact with opposite ends of the spring receptacles 13d and 14din a circular direction, respectively. Thus, the first and second powerinput plates 13 and 14 and the driven plate 19 are elastically coupledto each other in the circular direction, with the coil springs 22intervening between them. Under an idle state as shown in FIG. 24, eachof the seat elements 23 has its inner circumference alone put in contactwith ends of the spring receptacles 13a and 14a of the first and secondpower input plates 13 and 14 and an end of the window hole 19a of thedriven plate 19. This means the coil spring 22 is housed in the windowhole 19a and the spring receptacles 13a and 14a, being partially pushedagainst them.

The seat element 23 is supported by the flap 19b formed in the drivenplate 19. With such an element as the flap 19b, the driven plate candecrease bearing stress caused in supporting the coil spring 22 and theseat element 23, and its durability is improved. Consequently, it isneedless employing several sheet metal plates or disk plate of thickcasting parts as in the prior art. Thus, a weight of the driven plate isreduced and a cost is decreased.

The driven plate 19 is placed within the fluid space A, and hence, theflap 19b of the driven plate is lubricated by the viscous fluid. Thisresults in the flap 19b having improved durability.

The viscous resistance generator 25 will now be described. The viscousresistance generator 25 includes an annular housing 27 positioned in anoutermost circumference within the fluid space A, a plurality of pins 28coupling the annular housing 27 to the first and second power plates 13and 14 (see FIG. 24), and a plurality of sliders 29 arranged in theannular housing 27.

The annular housing 27 is positioned inside an outer circumferentialcylindrical wall of the second power input plate 14 and has its axiallyopposite end surfaces interposed between the first and second powerinput plates 13 and 14. The annular housing 27 is U-shaped in crosssection opening toward the engine, and as shown in FIGS. 26 and 27, itsinner circumferential surface close to the engine and the first powerinput plate 13 together define a gap 27a extending in a circulardirection. The outer circumference of the driven plate 19 is fitted inthe gap 27a. A plurality of stoppers 27b are formed at the sameintervals in the circular direction in and integral with the annularhousing 27. The stoppers 27b divide an annular fluid chamber B into aplurality of arched fluid sub-chambers B1. The stoppers 27b haverespective holes through which the pins 28 extend. Each of the pins 28has its opposite ends engaged with the first and second power inputplates 13 and 14 so as not to rotate by itself. This allows the annularhousing 27 to rotate along with the first and second power input plates13 and 14 in a unity.

Each of the stoppers 27b is provided with a choke C which is definedbetween an outer circumferential surface of the driven plate 19 and thestopper to connect each of the arched fluid chambers B1. The viscousfluid passing by the choke C causes a large viscous resistance.

A box-shaped resin slider 29 is placed within each of the arched fluidchamber B1, covering the projection 19c and flap 19d of the driven plate19. The slider 29 has its side closest to the engine opened. The slider29 has a face fitted in an inner circumferential surface of the annularhousing 27 and is movable in the circular direction in the arched fluidchamber B1. The slider 29, as shown in FIG. 27, has at an innercircumference close to the engine a notch 29a extending in the circulardirection. The projection 19c of the driven plate 19 passes through thenotch 29a and extends into the slider 29. Thus, the slider 29 is movablein the circular direction relative to the projection 19c and flap 19d ofthe driven plate 19 in a range where a wall in the circular direction isnot in contact with the flap 19d.

The slider 29 divide the arched fluid chamber B1 into a first cell 31 ona side designated as R2 and a second cell 32 on a side designated as R1.

An operation of the power transfer device will now be described.

When torque is received from the crankshaft 301 to the flexible plate 2,the first and second power input plates 13 and 14 and the coil springs22 transmit the torque to apply it to the driven plate 19. The torquereceived by the driven plate 19 is transmitted to the hub flange 3 viathe disk-like inertia element 40 till it is applied to the main driveshaft 302. Bending vibration contained in the torque transmitted fromthe crankshaft 301 is absorbed by the flexible plate 2.

An operation in the event that torsional vibration is transmitted fromthe crankshaft 301 to the damper 1 will be described. In the followingexplanation, the operation involves the torsional vibration transmittedbetween an power input system (the first and second power input plates13 and 14 and the annular housing 27) and a power output system (thedriven plate 19, the disk-like inertia element 40 and the hub flange 3).

It is now assumed that torsional vibration of a small torsional angle(minute vibration) at which a wall of the slider 29 in a circulardirection does not come in contact with the projection 19c and flap 19dof the driven plate 19 is transmitted. In such a situation, the annularhousing 27 and the slider 29 do not rotate relative to each other, andtherefore, the viscous fluid does not pass the choke C. In other words,during the minute vibration, a large viscous resistance does not arise.Also during the minute vibration, the coil spring 22 expands orcontracts, being partially pushed against the window hole 19a of thedriven plate 19 and the spring receptacles 13d and 14d of the first andsecond power input plates 13 and 14. Thus, a low rigidity is retained.Thus, under the minute vibration, characteristics of low rigidity andsmall viscous resistance are attained, and this is effective to suppressabnormal sound like clattering sound by the transmission or heavy sound.

An operation in the event that torsional vibration of a large torsionalangle (referred to as `grand vibration` hereinafter) is transmitted willbe described below.

When the wall of the slider 29 in the circular direction comes incontact with the flap 19d of the driven plate 19, the first cell 31 orthe second cell 32 is compressed between the slider 29 and the stopper27b. The viscous fluid flows from the compressed cell through the chokeC into adjacent fluid chambers B1. When the viscous fluid passes thechoke C, a large viscous resistance arises.

As mentioned above, during the grand vibration, a large viscousresistance is obtained. Additionally, as the torsional angle becomeslarger, the seat elements 23 on the coil spring 22 come to be in contactwith the end of the window hole 19a and the ends of the springreceptacles 13d and 14d of the first and second power input plates 13and 14, and thus, the rigidity is enhanced. Thus, during the grandvibration, characteristics of high rigidity and large viscous resistanceare attained, and this effectively dampens vibration upon tip-in-tip-out(large vibration forward and backward of an automobile caused by rapidoperation of an accelerating pedal).

It is assumed that the minute vibration is transmitted under thecondition that the annular housing 27 is displaced by a specified anglerelative to the driven plate 19. The slider 29 repeats reciprocaltorsional motions related to the flap 19d in an angular range where thewall of the slider 29 in the circular direction is in contact with theprojection 19c and flap 19d. In such a case, the viscous fluid does notflow at the choke C, and a large viscous resistance does not arise.Thus, even with a large torsional angle made between the annular housing27 and the driven plate 19, the minute vibration can be effectivelydampened.

When pressure is caused in the fluid space A because of viscousresistance or centrifugal force during the operation, the innercircumference 14a of the second power input plate 14 moves and comes incontact with an outer circumference of the annular projection 40a of thedisk-like inertia element 40. As a result, sealing is carried outbetween the second power input plate 14 and the disk-like inertiaelement 40. Since a seal element required in the prior art can beomitted in this embodiment, the power transfer device is structuraIlysimplified, and its cost is reduced.

Various modifications of the present invention can be devised withoutdeparting from the scope of the invention. The foregoing description isin all aspects illustrative, and it is not intended that the presentinvention be limited to precise forms disclosed in the appended claimsand equivalents thereto.

What is claimed is:
 1. A power coupling mechanism, comprising:a hubbeing connectable with an input shaft of a transmission; a driven platerigidly connected to said hub; a bearing supported on said hub; a driveplate supported on said bearing to allow for relative rotation betweensaid driven plate and said drive plate, said driven plate and said driveplate at least partially defining an annular housing; a vibrationdampening mechanism disposed within said annular housing between saiddrive plate and said driven plate elastically coupling said drive plateand said driven plate limiting relative rotary displacement between saiddrive plate and said driven plate; and an inertia element rigidlyconnected to said hub.
 2. The power coupling mechanism as in claim 1wherein said driven plate is rigidly connected to said hub by aplurality of axially extending rivets which extend through a portion ofsaid hub and a portion of said driven plate.
 3. The power couplingmechanism as in claim 1 wherein said driven plate and said inertiaelement are rigidly connected to said hub by a plurality of axiallyextending rivets which extend through a portion of said hub and aportion of said driven plate.
 4. The power coupling mechanism as setforth in claim 1, wherein said hub is formed with a radially extendingflange and said inertia element is connected to said flange.
 5. Thepower coupling mechanism as set forth in claim 1, wherein said hub isformed with a radially extending flange and said driven plate isconnected to said flange.
 6. The power coupling mechanism as set forthin claim 1, further comprising an annulus fixing element fixed to saiddrive plate, and wherein an inner race of said bearing is supported on aportion of said hub and an outer race of said bearing is mounted on saidannulus fixing element.
 7. The power coupling mechanism as set forth inclaim 1, further comprising a ring gear rigidly connected to saidinertia element.
 8. The power coupling mechanism as set forth in claim1, further comprising a second annular inertial element rigidly fixed tosaid drive plate proximate an outer peripheral portion thereof.
 9. Thepower coupling mechanism as set forth in claim 1, wherein said vibrationdampening mechanism comprises a spring member.
 10. The power couplingmechanism as set forth in claim 1, wherein:said drive plate being formedwith at least one axially extending annular protrusion which extendsinto said vibration dampening mechanism; said driven plate being formedwith at least one annular groove engaging and inter-fitting with saidannular protrusion such that engagement between said annular protrusionand said annular groove confines said driven plate against axialmovement with respect to said drive plate and provides structuralsupport against thrust and radial forces experienced by the powercoupling mechanism.
 11. The power coupling mechanism, as in claim 1,wherein said vibration dampening mechanism comprises a coil spring and aviscous fluid dampening mechanism.
 12. The power coupling mechanism, asin claim 1 wherein said vibration damper mechanism comprises a viscousfluid dampening mechanism.
 13. The power coupling mechanism as set forthin claim 12 wherein said drive plate is formed with at least one axiallyextending annular protrusion;said driven plate being formed with atleast one annular groove engaging and inter-fitting with said annularprotrusion such that engagement between said annular protrusion and saidannular groove confines said driven plate against axial movement andprovides structural support against thrust and radial forces.
 14. Thepower coupling mechanism as set forth in claim 1, wherein said hub isrigidly fixed to said driven plate, said bearing is supported on aportion of said hub such that an inner race of said bearing is mountedon a portion of said hub, an outer race of said bearing supports aportion of said drive plate.
 15. The power coupling mechanism as setforth in claim 1, wherein said inertia element has an annular discshape.
 16. The power coupling mechanism as set forth in claim 1, whereina portion of said inertia element has an annular disc shape and includesan annular portion at a radially outer portion thereof which protrudesin an axial direction at least partially encircling said annularhousing.
 17. The power coupling mechanism as set forth in claim 1,further comprising:a flex plate formed with a plurality of bolt holesfor connection to a crankshaft, said flex plate formed from asheet-metal material, said drive plate being connected to said flexplate.
 18. The power coupling mechanism as set forth in claim 17,wherein said bolt holes define a pitch circle and said bearing has anouter diameter smaller that said pitch circle.
 19. The power couplingmechanism as set forth in claim 17, wherein said drive plate isconnected to an outer peripheral portion of said flex plate.
 20. Thepower coupling mechanism as set forth in claim 17, wherein said inertiaelement is connected to said driven plate radially outward from saidpitch circle.
 21. A power coupling mechanism as set forth in claim 17,wherein said annular housing is formed with two opposing annularprotrusions, both of said opposing annular protrusions extending inaxial directions toward one another, and said driven plate is formedwith two annular grooves, each of said grooves on opposite axial facesthereof, said annular protrusions extending into said grooves radiallyand axially confining said driven plate with respect to said housing.22. A power coupling mechanism as set forth in claim 21 furthercomprising a power input plate, said drive plate and power input plateattached to one another and defining a fluid filled chambertherebetween.
 23. A power coupling mechanism as set forth in claim 1further comprising at least one cup-like slider slidably disposed withinsaid annular housing, said driven plate being formed with at least oneradially extending protrusion which extends into said cup-like slider,said slider defining two large cells within said annular housing andsaid protrusion defining two small cells within said cup-like slider,said housing and said large and small cells filled with viscous fluidsuch that fluid flows between adjacent cells in response to relativerotary displacement of said driven plate with respect to said driveplate.
 24. A power coupling mechanism for transmitting torque from arotary input shaft to a transmission shaft, comprising:a hub beingconnectable with a transmission shaft; a bearing supported on said hub;a pair of drive plates supported on said bearing to allow for relativerotation between said hub and said drive plates, said drive platesforming an annular housing therebetween; a driven plate connected tosaid hub, a portion of said driven plate extending into said annularhousing; a spring disposed within said annular housing elasticallycoupling said drive plate and said driven plate limiting relative rotarydisplacement between said drive plate and said driven plate; and aninertia element rigidly connected to said hub.
 25. The power couplingmechanism as in claim 24, further comprising:a second inertia memberattached to one of said drive plates; a flex plate connectable to arotary input shaft and to said second inertia member.
 26. The powercoupling mechanism as in claim 24, wherein said inertia element has anannular disc shape, said annular inertia element is disposed adjacent tosaid annular housing and said annular inertia element is rigidlyconnected to said hub.
 27. The power coupling mechanism as in claim 24,wherein said annular housing is fluid filled and a damper mechanism isdisposed in said annular housing, said damper mechanism includes aslider mechanism that dampens vibration in response to relative rotarydisplacement between said drive plates and said driven plate.